Finding your Latitude and Altitude for Barometer Corrections
  Online Resources

The National Map is an online, interactive map from the US Geological Survey. Select "Find Place" from the menu on the left to enter an address or place name, then zoom in for a closer view. You can add layers to the map, such as satellite images and topo maps, to help you pinpoint your exact location. Hover your cursor over your location on the map to read the latitude coordinate displayed just below the map. (The longitude coordinate is not required for your barometer corrections.) Clicking on "Elevation" in the left menu and then on your location on the map opens another window with your ground elevation information in addition to the coordinates.

Google Earth must be downloaded and installed on your computer. It is free for personal use. You can find your latitude, longitude (not needed), and ground elevation by entering an address or place name, then zooming in on detailed satellite photos and maps.

Paper Maps

You can get your latitude coordinate and ground elevation from many local maps of your area. The most detailed is usually the US Geological Survey 7.5 minute, 1:24,000-scale quadrangle series topo maps, available from local outfitter stores, some bookstores, your local BLM or Forest Service office, and from the USGS Online Store. Some public libraries may have topo maps available.

Introduction to Topographic Maps, a tutorial from the GeoSpatial Training and Analysis Cooperative, offers detailed information on understanding and using topo maps.

GPS

Commercial GPS (Global Positioning System) devices have built-in typical latitude errors of 120 to 180 feet which is good enough for the relatively small gravity correction, however the GPS typical elevation errors of 500 to 700 feet are much too large for barometry where errors ideally should not exceed one foot.

Read more . . .

Labels: barometric pressure, technical support

  posted by Jean Bergerot  8:35 AM