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Airspace Survey Utilizes World File Coordinates

 New Software Feature

May 1, 2002 we released a new version of Airspace Survey. This new version has a new GEOSearch engine for use on web server. It will initialize the server to select a Topographic Map or Aerial Photograph at a resolution of 24,000:1. This will enable you to drill down to your site to a resolution of 4 meters/pixel on the first click. We are also including a new startup map. This map was developed by USGS from radar data taken from the Space Shuttle. You can select a site by clicking on the map then "Jump" to the server.

In reaction to the changes to TerraServer web site Airspace Survey has been enhanced to read and calculate the calibration points of a topographic map or aerial photograph based upon the world coordinates provided by TerraServer web site. From the download page on the left side of the screen select "GIS World Coordinates." Please see the example
jump point below:

 How to work with UTM coordinates
LATITUDE: 38° - 53' - 06" (N)
LONGITUDE: 77° - 01' - 12" (W) 

Note:  This image is displayed at 1M Resolution

TerraServer_Sample_Image

This opens another browser window and you can save the file. Save it as a 'text' file format using the same or similar name as you saved the picture (topo/photo). The contents of the file is shown below:

1.000000 
0.000000 
0.000000 
-1.000000 
324200.000000 
4306400.000000

Next select the 'image info' link and note the 'Zone Number' under projection at the top of the screen. Please see the example below. If you used the JUMP capability of 'Get Point" or 'Set Point' the Zone Number is automatically calculated.

Note: Projection - The data below is projected in the Universal Transverse Mercator (UTM) Zone 18 projection using the North American datum of 1983. The decimal latitude and longitude in degrees and the UTM coordinates in meters are shown for each image tile.

You are now ready to calibrate the image using UTM World Coordinates.

Using Airspace Survey open the saved image.

Select File Menu and then Calibrate. The calibration window opens.

Airspace_Survey_Calibration

Select the "W" from the command buttons. This will open an Open File dialogue box where you select the world file (text) you saved earlier. After you open this file the calibration box will change displaying the world file coordinates.

World_Coordinates_Calibration

In this case the image is in Zone 18 at 1 meter/pixel resolution. The UTM coordinates for the upper left corner UTM coordinates of the image are shown. These need to be calculated into NAD83 Coordinates. To do this simply press the "U" command button and the calibration box will revert back to latitude and longitude. Now, as before, select "SAVE", "READ", and "CAL4" to complete the calibration process.