Since the Nation’s Capital was hit with a late Winter snow yesterday (2 March 2009), I was thinking about snow cover and available online sources mapping extent and depth of snow cover. The NOAA Snow and Ice Mapping System has daily updates on snow and ice cover and is easy to access, but does not have information on estimated snow depth. It is still a good resource if you are interested in snow cover, including historic data.

The Interactive Multisensor Snow and Ice Mapping System (IMS) (http://espcgis.nesdis.noaa.gov) provides analysis of snow and ice cover for the Northern Hemisphere at a 4 km resolution in an ESRI ArcIMS image map service. The main products page (http://www.natice.noaa.gov/ims/) provides access to the geospatially registered data in the web map service, as well as various gif images (see Figure 2) and time-animated image products that are maps but do not have world file georeferencing.

Figure 1. Interactive Map Webpage.

Figure 2. Ungeoreferenced GIF image example from 3 March 2009.

Data Listing (partial)

• Analyzed Snow and Ice from Satellites (SSDSnow)

 Access

Use of the ArcIMS interactive map interface is simple, and accessing the web map service is easy. 

Service Type: ESRI ArcIMS Image Service
Server Address: http://espcgis.nesdis.noaa.gov
Service Name: SSDSnowUsability

Figure 3. Snow/Ice data displayed overlaid in ArcGIS Explorer.

The data can also be directly consumed by clients that can read ESRI ArcIMS Image Map Services. The service has few layers and due to its light-weight is very responsize. it displayed very well in ArcGIS Explorer (build 500) over a cell data connection when the author was testing, see Figure 3). One minor issue if you are accessing the service via the interactive web map, is that the map is displayed in an unusual polar stereographic projection (see Figure 1), due to the fact that the system is focused on snow and ice cover for the Northern Hemisphere, it makes sense at least. 

Data Quality

The 4 km resolution is a bit limited, but for displaying snow/ice cover for regional views and even most States-level maps this service is certainly useful.  

Update Frequency 

Daily. 

Metadata

The  Analyzed Snow and Ice from Satellites (SSDSnow) layer has detailed metadata that even appears to be compliant with FGDC standards, unusual for a Federal data source.

Ratings

Accessibility Rating: Very Good

Usability Rating: Very Good

Data Quality Rating: Fair

Overall Rating: Good

Ratings on 5-pt scale (1- Poor, 2- Fair, 3- Good, 4- Very Good, 5- Excellent)

Introduction

The term GeoMAC stands for Geospatial Multi-Agency Coordination, and as such the web site is designed for support of multi-agency wildland fire situational awareness. Participating agencies include BLM, USFS, NPS, NIFC, CA Fire, among others. I will let you visit the GeoMAC web site for the full list of agency partners and the acronmy definitions.  The GeoMAC site is updated daily and therefore contains fairly current data about large wildfires being managed by the National Interagency Fire Center (NIFC).

Figure 1. GeoMAC Main Web Page.

During major wildfire flare-ups, GeoMAC can get a considerable amount of use. As case in point, during the 2007 October wildfires in California, the GeoMAC site was receiving so many hits during business hours that the interactive web map crawled to a halt, although accessing the web map services directly on the “back-end” still worked, albeit slower than normal. 

Data Listing (partial)

I have listed what I feel are the most relevant data layers available from the GeoMAC web map services.  In addition GeoMAC offers direct download of active and historical fire perimeters in shapefile and in Google Earth KML. 

Web Map Service Data Layers

• Current Fires
• Current Fire Perimeters
• MODIS Thermal Satellite fire detects
• HMS Thermal Satellite hot spots
• Historical Fires and Fire Perimeters

Downloadable Data Layers

• Active Fire Perimeters – KML
• Active Fire Perimeters – Shapefile

Access

Figure 2. GeoMAC Interactive Web Map Page

Access to all the features of the GeoMAC web site, including the web map services is free and open to the public.

As far as the primary data layers of interest (current and historical fires and perimeters and MODIS satellite data) there is little difference between the geomac and geomac_wms web map services.  Overall, it appears that the geomac_wms service has fewer base data layers.  Note that Alaska fire data is presented in a separate web map service of its own (geomacak).
 

• Service Type: ArcIMS Image Service
• Server Address: http://www.geomac.gov
• Service Name(s): geomac, geomac_wms, geomacak

Figure 3. GeoMAC Data Download Page

The data download is via from an ftp-like web page (see figure 3). This page is accessed via the “Download Perimeters” link on the entry page (see figure 1).

Usability

While my interest in and the purpose of this blog of geospatial data sources is primarily for use of geospatial data in GIS and similar software, it is worth noting that the GeoMAC web map has minimal functionality and many data layers in the web map service are not exposed in the web map interface. The data is best used when accessed via the web map services and can easily be ingested into ArcGIS Explorer and ArcGIS Desktop. The Current Fires and Perimeters overlaid well on your own base maps (when the GeoMAC base data is turned off)

Figure 4. GeoMAC web map service overlaid in ArcGIS Explorer

Figure 5. GeoMAC web map service as displayed in ArcGIS Desktop

 

Data Quality

Overall data quality is good, but there are some issues to be aware of.
 

The Current Fires point layer is maintained by the central office and therefore is generally not a very accurate location for the active fire (see figure 6 for a random example). In this example, the point for the fire is off by almost 4 miles from the historical fire perimeter. Fire perimeters are generally accurate in part because they were developed by the field staff at the site of the fire.  

Figure 6. Example of error in fire points versus fire perimeters using ArcGIS Desktop.

 

My other note about accuracy is regarding the thermal satellite fire/hot spot detections. The MODIS data is fairly useful, especially if current fire perimeters are not available for a given fire of interest, but the HMS data appears to have many false hits, by my assessment, so many as to make it worthless. 

The base data layers provided in the web map services are somewhat useful, but you will more than likely want to display the GeoMAC fire data over your own base map data.  

Update Frequency 

The current fire layer is updated daily. The fire perimeter data is updated periodically with data from the field offices (generally every 1-2 days), but it is important to note that they are not received for all fires. 

Metadata

FGDC compliant metadata is available for the historical data, but not for the more dynamic layers, such as Current Fires and Perimeters and the thermal satellite data. 

Ratings

Accessibility Rating: Excellent

Usability Rating: Very Good

Data Quality Rating: Good

Overall Rating: Very Good

Ratings on 5-pt scale (1- Poor, 2- Fair, 3- Good, 4- Very Good, 5- Excellent)

NOAA’s NowCoast web site (http://nowcoast.noaa.gov) has some very useful time-sensitive weather data. The data is available in ArcIMS Web Map Services, and can therefore be readily consumed by ESRI GIS software clients, but not so much by other geospatial tools. NOAA notes on the website that they have plans to create an OGC-compliant Web Map Service (WMS) as well as Web Feature Service (WFS) sometime in federal fiscal year 2008 (FY08); however, as of the review of the website by this author (8 Feb 2009), none was available.

Figure 1. NowCoast Webpage Initial Display - screen shot.

The NowCoast web map service includes many data layers and sources (too many to mention in entirety here). The service includes current weather station data, forecasts, and radar and satellite weather imagery. Weather station data includes current weather variables from Airports, Coastal-Marine Automated Network (C-MAN) Stations, NWS buoys, Gulf of Maine Ocean Observing System (GoMOOS) buoys, and NOS’ Physical Oceanographic Real-Time System (PORTS)… more acronyms than you can shake a stick at. Weather forecasts are linked from the web map service (with URLs) to various forecast web pages on the National Weather Service website (http://www.weather.gov) for County forecasts, Regional forecasts, and Marine forecasts.

Data Listing (partial)

• Current Observations
  • Air Temperature
  • Dew Point Temp
  • Wind Speed/Direction
    

    Figure 2. NowCoast example of available weather station data for New England Area.

  • Atmospheric Pressure
  • Visibility
  • Sea Surface Temp
  • Wave Height
  • Weather Radar images (NEXRAD)
  • GOES Visible and Infrared Cloud Cover images

• National Digitial Forecast Database (NDFD) (Gridded data for CONUS-only)
  • Temperature, MIN/MAX  (12 hour - 96 hour forecasts)
  • Relative Humidy (3-78 hrs)
  • Surface Wind Speed (3-78 hrs)
  • Wave Height (12-84 hrs)
  • Precipitation Amount (6-66 hrs)
  • Wind Speed/Vectors (3-78 hrs)

• Web “Weather” Cams
• Clickable links to various weather forecasts (Regional, Marine, Off-shore Marine)
• NWS Weather Alerts (short-fuse alerts and some long-fuse alerts)

Access

Access is open to the public. Instructions on connecting to the ArcIMS Image Service can be found on the NowCoast website by using the “Map Services” link at the top of the initial NowCoast webpage. The process for accessing is pretty straight-forward, and includes using the following URL (ttp://nowcoast.noaa.gov), and selecting the “NowCoast” service from the web map service listing in your application of choice.  

• Service Type: ArcIMS Image Service
• Server Address: http://nowcoast.noaa.gov/
• Service Name: nowcoast

Usability

The image service has many data layers and as a result is complex to use, although it is not beyond the ability of an experienced GIS professional. I have provided screen captures of some of the data from the NowCoast web map service using ArcGIS Explorer and ArcGIS Desktop (see figures 3 and 4). 

Figure 4. NowCoast web map service as initially displays in ArcGIS Desktop.

Figure 3. NowCoast Airport Weather Data displayed in ArcGIS Explorer.

Data Quality

Most of the data available is of good quality. Exceptions included the Web Cams layer, of which many of the links are broken, and the Weather Radar (NEXRAD) images, which are unfiltered for ground clutter. Better NEXRAD images are available from other web map services and web sites including some universities and commercial sources. 

Update Frequency 

Update interval varies, but is fairly frequent for much of the available data. As a case in point, the weather radar images (NEXRAD) have an update frequency of from 4-10 minutes (depending on the radar site supplying the data).

Metadata

Complete metadata does not seem to be available, but NOAA does provide what may be a more useful descriptive web page for each layer of data in the web map service. 

Ratings

Accessibility Rating: Fair

Usability Rating: Fair

Data Quality Rating: Very Good

Overall Rating: Very Good

Ratings on 5-pt scale (1- Poor, 2- Fair, 3- Good, 4- Very Good, 5- Excellent)