Help with Geo-referenced photos and GPS 1

[dvcrogers]

Guys and gals, I need your help in an aera I know nothing about.
I am running AutoCAD 2000(LDD 3 & ACAD map) and I am trying to insert aerial photos in a layer along with some GPS points from a surveyer.

I am having trouble getting the GPS "points" to overlay on the photos correctly.
I am using the same units for both; NAD 83

What I am doing is using map button, insert, (then I select the photo from the file with the coord. file in Word format)
Now, the GPS information is in an ACAD drawing already. I have tried to insert the photos into that drawing and I have tried to make the GPS "points" into a block and insert them into a new drawing with the photos already inserted.(without selecting a base point-letting ACAD do it)
Those attempts have failed. The GPS points are miles away from the area they were taken from.(according to where the photos are)

Any help would be great.

D. Rogers

 

[scotthicks99]

Are you SURE that the GPS coordinates are in the same horizontal coordinate system as the georeferenced picture? Just being NAD83 is not enough, as there are state plan coordinates that are NAD83 (northing and eastings) which can be in feet or meters and there are geographic coordinates that NAD83 (lat and long). There are also UTM coordinates systems. So, that is the first task...make sure you are in the right system...this will fix 90% of all of your problems.

Generally, the insert image commage on the map menu is pretty straight forward. Typically, georeferenced images are geotiffs and they usually have two files associated with them, one is .tif which is the actual image and a .tfw file which is basically a text file that assigns coordinates to the image. Both MUST have the same name prior to the file extension. Perhaps you moved or deleted this file.....

Good luck

 

[dvcrogers]

Scott, you made a good point about state plane coordinates. I need to dubble check that.
I have the text files with the same name.

I have a feeling the problem lies in the GPS points from the surveyer. These are in an ACAD drawing already so I dont know how I should check those or re-insert them correctly.

Thanks.

 

[TerryScan]

Check the metadata for your orthophoto and gps points for units as well.

I am in Delaware. We do survey work using state plane feet. Our state orthophoto inventory is in meters. You can check this by scaling the photo by 3.28083333 (U.S. survey feet in a meter).

For Map to successfully import this the first time:
1. make sure your drawing units are feet
2. Use the Image Insert in Map as you described, but be sure to select Meters for "insertion point and density" on the Source tab.

 

[dvcrogers]

Thanks for all the help. What was happening was the info that I had was in State plane and I was told that it was not.

I have one more question.
Can I draw at specific coordinates? I mean, if I have a Garmin GPS unit with a waypoint in it. Can I, draw a circle with the center at that waypoint's coordinates?