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Lately, the engineers are asking me to give them the area of the catchment area for drainage calculation. I use the USGS quads to map out the area and then I use various methods to compute the area. This is very approximate as the USGS quadrangle scale 1:24000. Is there a way to calibrate a map to a survey and grafically pick the hight-of-land points to get the area?
Yes.
1. get a raster image of the map, usually a .jpg, .gif, .tif, etc. Some of these come with their own world files that automatically position and scale the photo for you.
2. in a TPC drawing, choose Insert, Picture and follow the instructions to select the raster image file and insert the picture.
3. once inserted, right click the picture and choose Calibrate…
4. from the dialog, you can press F1 to get help and learn about calibrating, but basically, you will pick points on the photo that you have corresponding survey points for. Pick any number of these pairs of points and TPC will calibrate the photo to your survey.
5. now use the Add Points to Traverse… command and pick points from the photo as if your were digitizing the catchment area.
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