how can I geolocolized a .tif document?

[DavidKuliner]

this is my first question here, and I am not sure if I reached the right forum...

have a few .tif files which I would like to geolocalize before additin them to a navigation software.

would like to get some tips.

Thx

David

[OwenEarley]

Read up on the Fundamentals of Georeferencing in the ArcGIS help.

Once you understand the process you can use the georeferencing toolbar in ArcMap.

Make sure that you set the map projection to your desired output projection for the TIFF image - this will depend on the requirements of your navigation software.

You will also need to have some data in your map document that you can use for control points.

[DavidKuliner]

Thank you Owen...

will work according to your recommendations !

David

[NeilAyres]

Owen,

when geo-referencing a scanned map or similar, the data frame coord sys should be set to whatever coord sys the image is in. If you know what that is of course... Once geoereferenced, then the image can be used in any other coordinate system or exported / re-projected.

[OwenEarley]

the data frame coord sys should be set to whatever coord sys the image is in

This statement really depends on a number of factors:

• What coordinate system your input image uses (as you point out - if known).
• What coordinate system your control points are in (this should be known).
• What your desired output coordinate system is (this also should be known ).

In an ideal situation you have a known coordinate system for the input image that is the same as your control points and is also the coordinate system that you want for the output image. However, this is rarely the case.

[NeilAyres]

Owen,

well, yes I agree with you.

But if geo-reffing a scanned topo sheet for instance, some effort could be put into finding out what the sheet coord sys is, then use that. I always use an affine method (scale, shift, rotate) so that gives you a better idea if your guess at the coord sys is correct.

Very often I have seen people geo-reffing this sort of data directly into GCS (because its got corner text in DMS). This is wrong because the map is flat ie projected.