topic Re: Georeferencing CAD data, Link table not editing correctly in Data Management Questions

Georeferencing CAD data, Link table not editing correctly

ElizabethNagai — Fri, 26 Oct 2012 13:51:58 GMT

Hello,

I am working with a few CAD drawing files. I have created an esri_CAD.prj file with the geographic coordinate system (WGS 1984) in the folder where he CAD files are stored. Now, I need to georeference them.

I have coordinates for the corners of the files (they are rectangular tiles) in degrees minutes seconds. When I create a control point and click on the link table to edit the x y destination coordinates, it does not edit properly. For instance, if I type the x destination as "68:30:0.0E" the link table changes it to "68:0:0.0E". It is rounding all of the coordinates I enter to the nearest minute and this is making my georeferencing not make sense because the difference between the corners in the tile file are less than a minute.

Any help would be MUCH appreciated.

Thanks,
Beth

Re: Georeferencing CAD data, Link table not editing correctly

MelitaKennedy — Fri, 26 Oct 2012 14:56:30 GMT

Hi Beth,

I'm not 100% sure, but I think the link table wants decimal degrees, or xy values, as double precision values, not degrees-minutes-seconds. You may need to convert your corner values into decimal degrees.

Melita

Re: Georeferencing CAD data, Link table not editing correctly

ElizabethNagai — Fri, 26 Oct 2012 16:27:57 GMT

Hi Melita,

The link table has a box at the bottom which you can check for "Degrees Minutes Seconds". This displays all coordinates in degrees minutes seconds rather than decimal degrees. So I should be able to input either DMS or dd depending on whether the box is checked.

The main reason why I do not want to use decimal degrees is because when I convert my DMS into dd, it produces a repeating decimal that is infinitely long. For example, 16:40:0.0S converted to dd is -16.66666666....etc. If I round this number to a smaller number of digits, then the tiles I have are georeferenced but as a result, they do not align perfectly (the tiles are all slightly shifted and may overlap or have gaps between them). I don't know how to put a repeating decimal into the link table? Any solutions?

Thanks,
Beth

Re: Georeferencing CAD data, Link table not editing correctly

MelitaKennedy — Fri, 26 Oct 2012 18:33:01 GMT

Hi Beth,

Oh, I see it now. I think the DMS setting is for display only; at least, I haven't been able to get it to take any DMS values either interactively or through a link table. You might need to enter DD values (maybe via link tables where it'll be easier to edit?) and run the values out to 15-16 digits. That's double precision and the most that can get stored anyway. So:

34.66666666666667
12 34567890123456

Melita

Re: Georeferencing CAD data, Link table not editing correctly

ElizabethNagai — Sun, 28 Oct 2012 15:05:25 GMT

Hi Melita,

Thanks for your reply.

It appears that when I edit the link table and try to add a number with 15-16 digits, it rounds it to 6 decimal points.

As a result, the tiles are still slightly misaligning. I'm really lost for ideas, please let me know if there's any solutions you can think of.

Thanks,
Beth