5.1 Siting Considerations
The primary purpose for siting ESSs near roadways is to measure weather and pavement conditions on or adjacent to the roadway. These measurements are subsequently used to support management decisions and the prediction of future road and weather conditions detrimental to the safe operations of vehicles on the road. There are many obstacles that must be overcome for the proper siting of those stations.
The most difficult aspect of proper siting is to ensure that the sensor locations provide the specific road weather information required. This is not possible in all cases due to physical obstructions, safety, or security issues. In most cases, siting to satisfy the requirements for proper operation of one sensor can be accomplished, but the site may prove inappropriate for measurement of other desired conditions. In such cases, critical compromises or additional actions may be required to locate an ESS. Care must be taken to ensure compromises do not result in locating an ESS or ESS sensor in a location that will not be representative of the required road weather conditions. To avoid such situations, additional sensors or additional sites should be considered.
In addition to close proximity to the roadway, the sensors should be selected relative to the environment being monitored. If the intent is to measure winds of hurricane strength, then the instruments need to be of sufficient durability to handle the expected conditions. Additional actions may include adding sensors of identical types to an ESS in order to satisfy multiple requirements at a single location, e.g., installing a wind sensor on a bridge separate from one sited nearby in an open unobstructed area. The use of additional sensors will help ensure each is representative of the area or location of interest, but this will normally increase system costs and complexity.
Siting decisions should be based on the need for specific road weather information. Planning should address data requirements first; then address how to satisfy power and communications requirements.
5.2 Power
All sensors require some level of power to operate (e.g., signal voltages, sampling cycles, storage of data, and possibly heating elements). Power is also required for the collection of the data at the RPU and for transmission of the road weather data to its intended users. Power options include commercial power, wind power, or solar power with batteries.
The selection of the appropriate power option is dependent on the availability and dependability of the source. A commercial power connection is usually the most economical and reliable source of power. Solar power can support nominal loads but is typically not capable of sustaining heavy power consumption for heated sensors. Figure 9 illustrates two options for mounting solar panels. Care should be taken to ensure solar panels do not block or interfere with the operation of the atmospheric sensors. If the cost to physically connect to a direct, dedicated electric source is prohibitive, other options must be considered. The actual selection of the power source may subsequently dictate which sensors can be supported.
Figure 9. Options for Mounting Solar Panels
Cost becomes a factor in the decision of whether to install less expensive sensors or communications requiring little power versus more capable sensors or communications requiring more power. Efforts should be made to ensure power considerations do not jeopardize the usefulness of the ESS. The use of solar power is more common in the western and southwestern United States where there is more ample sunlight. Commercial power, requiring less maintenance but considerably more installation costs, is used in most other areas. The use of wind power has been successfully implemented for a number of ESS installations in North Dakota.
5.3 Communications
Similarly, tradeoffs in the method and equipment to support timely and effective data communications (e.g., report frequency versus cost) may also have to be made, hopefully without compromising the usefulness of the ESS.
Communications options include hardwired telephone, cellular, copper wire, fiber optic cable, wireless, radio, microwave, or satellite. An important factor in the selection of the communication method and equipment is the amount of data that will be required to pass from the RPU. This will be a function of how much data are included in each observation (e.g., bandwidth considerations) and how often observations are transmitted (e.g., report frequency). For sites with low bandwidth requirements (i.e., no video camera and infrequent reporting), a polling system using telephone lines or some type of wireless communication may be more economical than hardwired options. In some cases, ESS siting decisions will be affected by line-of-sight and terrain shadowing considerations. For high data volumes, a hardwired communication system (wire or optical fiber) appears more appropriate, although installation costs could be increased considerably. DOTs should consider using “historical” polling of road weather data, if the RWIS RPU can support it. With historical polling, road weather data are stored in the RPU and are retrieved at set times (e.g., at the top of the hour and every 15 minutes thereafter). This process differs from polling the RPU to get only the current road weather observation. Employing historical polling enables the DOT to recover earlier road weather observations if communications’ failures interrupt the polling process.
A complete analysis of communication options and possible interfaces with the present or planned ITS should be performed early in the siting process. In some cases, ESSs can be located near other ITS devices (e.g., traffic counters, dynamic message signs, traffic signal controllers, bridge anti-icing systems) to share power and communications costs. For critical sites, backup sources of power or communications may be needed. An analysis of communications should also consider the weather information requirements of partnering agencies, such as NWS. Partnering agencies may need weather observations at a greater reporting frequency than the DOT. Such requirements may influence the communications solution.
5.4 Aesthetics, Maintenance, Safety, and Security
In some cases, ESSs have been moved or painted in order to minimize how much they stand out from the surrounding terrain and vegetation. Unfortunately, following the siting criteria related to maintaining adequate distances from obstructions can result in a sensor tower that is very obvious. Pre-siting discussions with the surrounding stakeholders can possibly forestall any aesthetics problems.
Pre-siting analysis should also review potential sites for environmental and archaeological significance.
Siting must, in all cases, acknowledge and be subject to safety clear zones.
Geological considerations may impact siting. Soil mechanics may affect placement of access ways, base pads, and subsurface sensors. Stormwater management is important to both the accuracy of meteorological observations and site maintenance. The National Pollutant Discharge Elimination System (NPDES) Stormwater Guide (US Environmental Protection Agency. Stormwater Guide. National Pollutant Discharge Elimination System. www.epa.gov/npdes/pubs/sw_swppp_guide.pdf) may be used as a reference or basis for stormwater management at the ESS site.
Maintainability of the ESS should be a consideration in both site location and design. Siting too close or too far from the roadway may seriously complicate maintenance procedures or unnecessarily jeopardize maintenance personnel safety. Installations too close to the pavement may make the data more representative of the actual roadway conditions, but increase the hazard to maintenance personnel. Installations too far from the roadway may decrease the value of the data by making the data unrepresentative of the roadway environment. Site design must also include analysis of access to sensors for either fixed-base towers within the enclosure or along the length of a fold-over tower. Maintainability may be enhanced by including remote ESS site monitoring capabilities as part of the RWIS.
Extra security measures should be taken in areas where the threat of vandalism is present. These may include a security fence around the ESS, anti-climb panels, or even security cameras.
5.5 Periodic Siting Reevaluation
An important consideration of any ESS is the periodic reevaluation of the site. Over the years, construction projects, both on and off the roadway, and vegetation growth can change the representativeness and usefulness of ESS locations. A periodic reevaluation of the site is needed to ensure that the observation data from the site are still valid and that the metadata on the site are still correct. Obstructions should be reevaluated for interference and, if required, a new site should be determined or obstructions removed. Any changes resulting from this reevaluation should be included in updated entries to the site and sensor metadata in order to maintain a valid history of the site and its sensors. This reevaluation can be accomplished as part of an annual preventive maintenance program needed for sensor maintenance and calibration.
5.6 Siting Metadata
An important aspect of the effective use of road weather data from ESSs is the documentation and distribution of the site’s metadata. Metadata is basically defined as “data about data.” In the case of the RWIS ESS, metadata should include the station and sensor locations, the history of any changes in the metadata, and a representative index for the particular location and its sensors. The metadata is used to document the characteristics of each sensor and its siting to provide users a better understanding of what the sensor data really represent. The Federal Geographic Data Committee (FGDC) has developed standards for digital geospatial metadata (Federal Geographic Data Committee, Content Standard for Digital Geospatial Metadata, FGDC-STD-001-1998). The referenced document provides “a common set of terminology and definitions for the documentation of digital geospatial data.” A companion document (Federal Geographic Data Committee, Content Standard for Digital Geospatial Metadata Workbook, Version 2.0 May 1, 2000) describes how and why a uniform set of criteria or standard was developed and presents it in more detail. David Hart and Hugh Phillips also have published a primer on metadata use (Hart, D and H. Phillips, Metadata Primer – A “How To” Guide on Metadata Implementation, University of Wisconsin website). Currently, there are no corresponding uniform recommendations for RWIS ESS location and sensor metadata.
Various forms of metadata currently exist for ESSs that are not components of RWIS. The National Climatic Data Center (NCDC) maintains metadata for a number of its datasets. These datasets include: (1) Climate Reference Network dataset (US Department of Commerce, National Climatic Data Center, United States Climate Reference Network (USCRN) Metadata Management – Survey to Operations (Draft). June 2003), (2) NCDC Station History Database with approximately 30,000 stations and part of the NCDC Station History Information Processing System (SHIPS) (US Department of Commerce, National Climatic Data Center, Data Documentation for Data Set 9767B, Master Station History Report. December 31, 2002), and (3) NWS Cooperative dataset (Viront-Lazar, A. and P. Seurer, Metadata for Climate Data, A Geographic Data Base Model for Station History, First IEEE Metadata Conference, April 16-18, 1996). The elements for the NCDC station metadata, accessible through their Master Station History Report, include station identification with a number of identifiers; location (e.g., country and state); latitude/longitude; station name; period of record; elevation; and, station type. Elements for the cooperative sites include exposure, topography, and driving directions. The SHIPS database also contains more detailed information about the observations and instrumentation for some locations. In addition, development of a common set of metadata requirements for the NWS National Cooperative Mesonet, a part of the NWS Integrated Surface Observing System (ISOS) Program, is currently underway. The ISOS program may include RWIS as part of the national mesonet. To be included, RWIS data will need to have a minimum set of metadata for each site. Although still being finalized, this metadata set includes platform owner, station name and identifier, station coordinates, station elevation, observed elements with their units, station reporting frequency, and an observation timestamp description. All of these metadata items are included in the recommended ESS metadata set listed in Table 2. As metadata requirements become finalized for the NWS ISOS Program, RWIS metadata managers may want to adjust their metadata archive accordingly.
Currently procedures for archiving ESS metadata vary from state to state. To maximize the application of ESS data within the transportation community and by other potential users, uniformity in metadata content and formats is encouraged. At a minimum, those items with a history of changes should be collected, centrally stored, and backed up whenever a change occurs. In addition to the collection and storage of the metadata, the metadata should also be readily available to any individual or agency that uses the data. The effective distribution of metadata is just as important as the distribution of the sensor data. This distribution of metadata is necessary to ensure that the user understands the characteristics of the road weather data, e.g., whether it is designed to monitor the conditions at a specific site for a specific local purpose or whether that data is designed for general surface transportation weather observing and forecasting.
Recommended metadata items for ESSs are listed in Table 2. Additional metadata items, listed in Table 3, can provide more useful information to road weather data users. Some items in the metadata sets in Tables 2 and 3 correspond directly to identification objects listed in the National Transportation Communications for ITS Protocol (NTCIP) Standard for ESS objects (US Department of Transportation. National Transportation Communications for ITS Protocol (NTCIP) – Object Definitions for Environmental Sensor Stations NTCIP 1204. November 23, 2001. Release of Version 2 is expected in 2005).
Table 2. Critical ESS Metadata
Field Name |
Field Description |
Data Type |
Example |
| climateRecord |
climateRecord |
climateRecord |
climateRecord |
minObsRecord |
The minimum observed value of this observation type for this period (month). Precision & bounds dependent on data type
Critical - but not necessarily owner provided |
real |
Minimum Monthly Temp (in Deg C) = -2.9 |
maxObsRecord |
The maximum observed value of this observation type for this period (month). Precision & bounds dependent on data type
Critical - but not necessarily owner provided |
real |
Maximum Monthly Temp (in Deg C) = 38.2 |
period |
The month to which this climate record applies (1=Jan ... 12=Dec)
Critical - but not necessarily owner provided |
integer |
May = 5 |
collector (data access to the RWIS) |
collector (data access to the RWIS) |
collector (data access to the RWIS) |
collector (data access to the RWIS) |
protocol |
Description (in lower case) of the protocol used to retrieve observations (examples of input include: ftp, http, or https) |
text(10) |
https |
hostName |
The network DNS name or IP address of the collector host server |
text(50) |
www.fhwa.dot.gov or 64.126.107.233 |
hostPort |
The logical network address port on the collector host server
Critical - if required by owner |
integer |
http = 80, ftp = 22, https = 443, or owner defined integer |
fileLocator |
The logical directory path to the observation file |
text(50) |
path = /stateDOT/RWIS/obs/ |
filename |
The filename or the rule for generating file names that contain the observations |
text(50) |
ESS_Observations.txt |
username |
The identifier name that is used to log into the collector host server
Critical - if required by owner |
text(50) |
username = Name |
password |
The password that is used to log into the collector host server
Critical - if required by owner |
text(50) |
password = iHavePermission |
obsCollFreq |
The number of minutes between collection cycles at the agency's collector host server (when a new file is ready for retrieval). Maximum allowed is 60 minutes. |
integer |
minutes = 13 |
obsCollOffset |
The number of minutes after midnight UTC that the first collection occurs (for Clarus retrieval purposes). Minutes range from 0-60. |
integer |
minutes = 2 |
UTCOffset |
The number of minutes offset from UTC for the agency's collector host server in Standard time. Areas in the U.S. (west of Greenwich) use negative values. Valid range is -720 to +720 minutes. |
integer |
minutes = -240 |
DST |
Daylight Savings Time on the server is observed (True or False) |
bit |
1=True, 0=False |
startDST |
Starting date and time for DST
Critical - only if DST field is TRUE |
datetime |
4/12/2006 2:00 |
endDST |
Ending date and time for DST
Critical - only if DST field is TRUE |
datetime |
10/15/2006 14:15 |
collectorConfig
Describes the format of the DOT weather data file;
one set of entries is required for each observation type in the file |
collectorConfig
Describes the format of the DOT weather data file;
one set of entries is required for each observation type in the file |
collectorConfig
Describes the format of the DOT weather data file;
one set of entries is required for each observation type in the file |
collectorConfig
Describes the format of the DOT weather data file;
one set of entries is required for each observation type in the file |
headerIndex |
The positional order (comma delimited) of observation type in the collected observation file (leftmost column = 1) |
integer |
the temperature column = 5 |
receiveUnits |
Type of units for conversion purposes; Most 1204 units are included |
text(50) |
Degrees Celsius |
receiveLabel |
Column label name from collected observation file |
text(50) |
column = AirTemp |
unitsMultiplier |
The multiplier used to adjust the decimal position (e.g., multiply 209 by 0.1 to get 20.9 Deg C) |
real |
times 0.1 |
metadata contact information (from agency) |
metadata contact information (from agency) |
metadata contact information (from agency) |
metadata contact information (from agency) |
name |
Contact person
Critical - administrator access only |
text(50) |
Mr. Fred Flintstone |
title |
Contact person title
Critical - administrator access only |
text(50) |
Owner of the Bedrock Mesonet |
phonePrimary |
Contact phone (including area code)
Critical - administrator access only |
text(10) |
2025551301 (no dashes) |
email |
Contact email address
Critical - administrator access only |
text(50) |
Fred.Flintstone@bedrock.com |
contributor |
contributor |
contributor |
contributor |
name |
Name of the contributing agency or group within the agency providing observations
Critical - administrator access only |
text(50) |
Bedrock Quarry Company |
contactName |
Contact person
Critical - administrator access only |
text(50) |
Mr. Barney Rubble |
title |
Contact person title
Critical - administrator access only |
text(50) |
Bedrock Mesonet Operator |
phonePrimary |
Contact phone (including area code)
Critical - administrator access only |
text(10) |
2025551302 (no dashes) |
email |
Contact email address
Critical - administrator access only |
text(50) |
Barney.Rubble@bedrock.com |
organization |
organization |
organization |
organization |
name |
Organization name
Critical - administrator access only |
text(50) |
Loyal Order of Water Buffalo |
contactName |
Contact person
Critical - administrator access only |
text(50) |
Mr. Slate |
title |
Contact person title
Critical - administrator access only |
text(50) |
Organization that owns the Bedrock Quarry |
phonePrimary |
Contact phone (including area code)
Critical - administrator access only |
text(10) |
2025551300 (no dashes) |
email |
Contact email address
Critical - administrator access only |
text(50) |
Slate@bedrock.com |
sensor-specific information |
sensor-specific information |
sensor-specific information |
sensor-specific information |
obsType |
Type of observation collected by this sensor; based on NTCIP 1204 types (see 1204 worksheet) |
text(50) |
essAirTemperature |
sensorIndex |
The order of like sensors; used to distinguish one of a set of like sensors associated with a particular station |
integer |
when multiple sensors are involved at one station: puck 0, puck 1, puck 2, puck 3 |
minRange |
Minimum value for sensor range (hardware) test, as defined by the sensor manufacturer or the instrument owner |
real |
minimum sensor range temp = -160.0 Degrees or the minimum sensor range temp set by the operator = -100.00 (whichever is most restrictive) |
maxRange |
Maximum value for sensor range (hardware) test, as defined by the sensor manufacturer or the instrument owner |
real |
maximum sensor range temp = 220.0 or maximum sensor range temp reporting = 150.0 (whichever is most restrictive) |
distGroup |
Identifies distribution group to whom data from this sensor can be provided |
integer |
1 = DON'T distribute, 2 = distribute to everyone, etc. |
ratePos |
Maximum positive rate of change during the time period defined by rateInterval, and as used by step test
Critical - but not necessarily owner provided |
real |
20.0 degrees |
rateNeg |
Maximum negative rate of change during the time period defined by rateInterval, and as used by step test; reported as a negative number
Critical - but not necessarily owner provided |
real |
-20.0 degrees |
rateInterval |
Interval of time, in seconds, over which ratePos & rateNeg apply in the step test
Critical - but not necessarily owner provided |
real |
3600.0 seconds or 1 hour |
persistInterval |
Amount of time, in seconds, that the observed value can remain constant (not change). Used for the persistence test
Critical - but not necessarily owner provided |
real |
14000.0 seconds or 4 hours |
persistThreshold |
Smallest amount of change that is allowed between observations. Used for the persistence test
Critical - but not necessarily owner provided |
real |
0.2 degrees |
likeThreshold |
Largest observed difference that is permitted among like instruments. Used during the like instrument test
Critical - but not necessarily owner provided |
real |
1.0 degree |
sensorType |
sensorType |
sensorType |
sensorType |
mfr |
Manufacturer of sensor |
text(50) |
Vaisala |
model |
Manufacturer's model number of sensor |
text(50) |
DSC111 |
site-specific information |
site-specific information |
site-specific information |
site-specific information |
description |
Description of site, as used by the contributor (e.g., "Seward Highway @ Portage Glacier Road") |
text(50) |
Fairfax County Parkway @ Reston Avenue |
stateSiteId |
Contributor's identifier for the site
Critical - but not necessarily owner provided |
text(50) |
stateSiteId = 315 |
station-specific information |
station-specific information |
station-specific information |
station-specific information |
category |
The category of station - "P" permanent, "T" transportable, "M" mobile, "O" other |
text(1) |
P |
stationCode |
The contributor's station identifier; this may be different than the stateSiteID to allow more than one station at a given site |
text(50) |
stationCode = 48 |
rpuUTCOffset |
The number of minutes offset from UTC for the remote processing unit (RPU). Areas in the U.S. (west of Greenwich) use negative values. Range from -720 to +720 |
integer |
-60 |
rpuDST |
Does the RPU need adjustment for Daylight Savings Time(DST)? [(0=no, 1=yes] |
bit |
1 |
rpuStartDST |
Starting date and time for DST (for the RPU)
Critical - only if rpuDST field is TRUE |
datetime |
4/12/2006 2:00 |
rpuEndDST |
Ending date and time for DST (for the RPU)
Critical - only if rpuDST field is TRUE |
datetime |
10/15/2006 14:15 |
locBaseLat |
The latitude location of the base of the station tower or RPU stand, in decimal degrees (e.g., 34.567); positive values are North latitudes. Value can hold up to 9 digits of precision |
real |
37.4821 |
locBaseLong |
The longitude location of the base of the station tower or RPU stand, in decimal degrees (e.g., -123.456); negative values are West longitudes. Value can hold up to 9 digits of precision |
real |
-113.22 |
locBaseElev |
The elevation location of the station base (tower or RPU stand) in meters from mean sea level |
real |
135.5 |
Table 3. Supplemental ESS Metadata
Field Name |
Description |
Data Type |
Example |
collector (data access to RWIS) |
collector (data access to RWIS) |
collector (data access to RWIS) |
collector (data access to RWIS) |
description |
Description of collector |
text(50) |
This collector will work with all ESS on the XX DOT network |
maintInstallDate |
Date of initial installation |
datetime |
5/4/2003 12:24 |
mfrName |
The name of manufacturer |
text(50) |
Facundo Computing |
mfrProduct |
The name of the product |
text(50) |
JF Blade Series 1000 |
mfrModel |
The model number or software version |
text(50) |
123456HH0JM2 |
Supplemental contact information (Network Owner) |
Supplemental contact information (Network Owner) |
Supplemental contact information (Network Owner) |
Supplemental contact information (Network Owner) |
phoneAlt |
Contact phone alternate (including area code) |
text(10) |
2025551212 (no dashes) |
phoneMobile |
Contact mobile phone number (including area code) |
text(10) |
2025554444 (no dashes) |
fax |
Contact phone fax (including area code) |
text(10) |
2025553333 (no dashes) |
pagerId |
Contact pager identifier |
text(10) |
2025551111 (no dashes) |
pager |
Contact pager number |
text(10) |
556687 |
radioUnit |
Contact radio unit identifier |
text(50) |
2025555555 (no dashes) |
address1 |
Contact mailing address line1 |
text(50) |
123 1st Street |
address2 |
Contact mailing address line2 |
text(50) |
Suite 450 |
city |
Contact mailing address city |
text(50) |
Apple |
state |
Contact mailing address state |
text(2) |
OR |
zip |
Contact mailing address zip |
text(10) |
99999-4444 |
country |
Contact mailing address country |
text(3) |
USA |
Contributing organization |
Contributing organization |
Contributing organization |
Contributing organization |
location |
Organization location |
text(50) |
MODOT |
purpose |
Organization purpose |
text(50) |
To provide a world-class transportation experience that delights our customers and promotes a prosperous Missouri. |
centerId |
Organization center identifier |
text(50) |
4 |
centerName |
Organization center name |
text(50) |
KC Scout |
updateDate |
Organization information last updated |
datetime |
10/23/2005 14:25 |
contactId |
Contact identifier |
integer |
Contact name for organizational issues that is included in the contact list - the id of the contact name will be put here |
Sensor-specific information |
Sensor-specific information |
Sensor-specific information |
Sensor-specific information |
calibDate |
The last date of calibration of the sensor
Recommended for owner maintenance records |
datetime |
9/3/2006 10:30 |
maintDate |
The last date of maintenance performed on the sensor
Recommended for owner maintenance records |
datetime |
9/4/2006 4:00 |
serial |
Manufacturer's serial number for sensor
Recommended for owner maintenance records |
text(50) |
55335668 |
resolution |
The smallest increment or measurement that can be obtained from a particular sensor |
real |
tenths of degrees = .1 |
accuracy |
The known potential variation of the observation |
real |
0.05 |
minDisplay |
Minimum value for sensor display |
real |
-52.85 |
maxDisplay |
Maximum value for sensor display |
real |
120.22 |
nsOffset |
The north/south distance from the station reference location in meters |
real |
15.0 meters |
ewOffset |
The east/west distance from the station reference location in meters |
real |
8.0 meters |
elevOffset |
The vertical distance from the station reference location in meters |
real |
3.0 meters |
surfaceOffset |
The vertical distance from the pavement surface in meters |
real |
0.5 meters |
embeddedMaterial |
Description (including depth) of material sensor is embedded in. |
text(100) |
rubber cement |
outputAvgInterval |
Milliseconds used to describe average interval of observations |
integer |
300,000 milliseconds = 5 minutes |
outputInternalUnits |
Internal units reported to data logger |
text(8) |
Celsius |
maintInstall |
Initial installation date for sensor
Recommended for owner maintenance records |
datetime |
2/8/2003 8:45 |
maintBegin |
Date sensor is taken out of service; sensors for which maintBegin < currentDate < maintEnd will not be checked for data quality. Use if sensor will be out of service for a significant period of time. |
datetime |
10/15/2006 14:15 |
maintEnd |
Date sensor is put back into service; sensors for which maintBegin < currentDate < maintEnd will not be checked for data quality |
datetime |
10/15/2006 18:15 |
samplingInterval |
Interval time, in seconds, between consecutive sensor readings |
real |
15.0 seconds |
sensorDescription |
Plain text description of the sensor (e.g., thermometer, CCTV camera) |
text(100) |
PTZ fixed IR camera |
linkURL |
Link to CCTV images
Optional - unless the sensor is a CCTV then mandatory |
text(255) |
Direct URL link to a CCTV image |
Site-specific information |
Site-specific information |
Site-specific information |
Site-specific information |
roadwayDesc |
Name/number of the highway nearest to the site (e.g., "Interstate 35," "U.S. Hwy 59," "State Hwy 81," "Haines Highway") |
text(50) |
State Hwy 81 |
roadwayMilepost |
Nearest mile marker to the site |
integer |
45 |
roadwayMilepostUnits |
Units reported for roadwayMilepost
Optional - but must be included if roadwayMilepost is used |
text(50) |
Miles |
roadwayOffset |
The distance, in meters, between the closest point on the center surface of the roadway to the site reference point (e.g., base of an RWIS station) |
real |
37.53 meters |
roadwayHeight |
The elevation difference, in meters, between the closest point on the center surface of the roadway to the site reference point (e.g., base of an RWIS station) |
real |
22.8 meters |
county |
The county or jurisdictional name of the site location |
text(100) |
Fairfax County or Centreville Township |
state |
State of the site location (2 letter postal ID) |
text(2) |
VA |
country |
The country of the site location (e.g., USA, CA, MX) |
text(3) |
USA |
accessDirections |
Directions to access the site from a major roadway
Recommended for owner maintenance records |
text(50) |
Turn left at the cow, proceed three miles to Joe's Grocery, turn right on State Hwy 81, go 3 miles, on left |
representativeness |
Describe any unique meteorological or topographical feature(s). |
text(255) |
Between 2 & 4 PM during the summer months, the ESS is shaded |
obstructions |
Description of physical properties (e.g., trees, buildings) that might affect the accuracy of observations |
text(100) |
Large outhouse parked on SW side of ESS |
landscape |
Description of surrounding landscape |
text(100) |
sandy area except for obstruction of oak tree and outhouse |
accessControlled |
Ability for contributor to access the site (e.g., locked fence around site) |
bit |
0 = no access, 1 = full access |
terrainSlope |
The grade of the surrounding land, in whole degrees from horizontal |
integer |
10 degrees |
terrainSlopeDirection |
The direction of the grade, in degrees from North (e.g., slope down from west to east is noted as 270) |
integer |
85 degrees |
windRoughnessClass |
Roughness of the wind in four directions (expressed in whole percent) |
text(50) |
24 percent |
soilType |
The type of soil on which the site is located, as described by the USDA National Resource Conservation Service soil texture classification (e.g., sandy loam, silt) or by percent sand, silt, and clay |
integer |
Full enumeration list is not yet available |
stateSystemId |
Site identifier used by the State DOT (or other data contributor) |
text(45) |
22 |
linearReference |
Linear reference marker number |
real |
4.3 |
Station-specific information |
Station-specific information |
Station-specific information |
Station-specific information |
description |
The description of the station |
text(100) |
The ESS has a 30 m tower with 10 sensors |
type |
The type of station - "0" data collected electronically/mechanically, "1" collected by humans, "3" type of station is unknown |
integer |
0 |
locBaseDatum |
The datum geocoordinate referencing model |
text(10) |
WGS 1984 |
powerType |
The type of power for the station - "B" battery, "L" line
Recommended for owner maintenance records |
text(1) |
B |
doorOpen |
The status of the door (0=closed, 1=open) |
bit |
0 |
batteryStatus |
The percentage of full charge of the battery (101 = error) |
integer |
78 |
lineVolts |
The typical voltage for the power source (0 to 100) |
integer |
12 volts |
maintArea |
The description of the maintenance group for this station (for the site maintenance personnel) |
text(50) |
Substation 52 |
maintPrevFreq |
The description of preventative maintenance intervals
Recommended for owner maintenance records |
text(50) |
The station is serviced every year in the spring or when the station fails completely |
maintCalibFreq |
The description of the calibration maintenance intervals
Recommended for owner maintenance records |
text(50) |
The station is calibrated every spring and fall |
maintStatus |
The maintenance status of the station - "0" out of service, "1" in service
Recommended for owner maintenance records |
bit |
0 |
maintInstallDate |
The initial installation date of the station
Recommended for owner maintenance records |
datetime |
3/8/2004 8:00 |
rpuNumCards |
The number of sensor interface devices |
integer |
2 |
rpuCommType |
The communication type for the station - "1" phone, "2" IP address
Recommended for owner maintenance records |
integer |
2 |
rpuPhoneNum |
The phone number to contact the rpu
Recommended for owner maintenance records |
text(10) |
2025555555 |
rpuIPAddress |
The IP address to contact the rpu
Recommended for owner maintenance records |
text(15) |
64.126.107.233 |
rpuMfr |
The manufacturer of the rpu |
text(50) |
XYZ Manufacturer |
obsCollFreq |
The number of minutes between collection cycles (rpu to agency server) |
integer |
2 minutes |
obsCollOffset |
The number of minutes after UTC midnight that the first collection occurs |
integer |
1 minute |
obsTransFreq |
The number of minutes between transmission cycles |
integer |
15 minutes |
obsTransOffset |
The number of minutes after UTC midnight that the first transmission occurs |
integer |
16 minutes |
obsTransFormat |
The description of the transmission format from the station to the network data logger |
text(50) |
The ESS will communicate with the data logger by way of remote control |
maintContactId |
The contact person for maintenance from contact table; is implemented in the database as a link to a contact person |
integer |
Contact name for maintenance issues that is included in the contact list - the id of the contact name will be put here |
Image information |
Image information |
Image information |
Image information |
description |
Description of image |
text(50) |
The image represents the Cumberland Pass in southwest Virginia |
linkURL |
URL for image
Optional - but must be included if image description is provided |
text(255) |
www.i70ess248.gov |
By establishing, maintaining, and sharing a robust metadata archive for ESS sites and their sensors, both transportation and other users will be able to effectively apply the ESS data to their particular weather and road weather information requirements.
