[GRASS-user] Orthorectifying images

[Markus Metz]

katrin eggert wrote:
> Hello Markus
> Thank you for your answer. Just a few more questions :)
>
>>
>> There is no preprocessing required before orthorectification, apart
>> from the organisation of the imagery. The imagery to be orthorectified
>> should be in a xy location. A separate location with the target CRS
>> must exist and should hold reference imagery if you do not have Ground
>> Control Points.
>>
> 1- My VHR image has already coordinates. Is this a problem?

No. Sorry for the confusion, usually the imagery to be georectified
comes without any CRS and thus goes into a xy coordinate system. If
the imagery already has a CRS, you can use that, and source and target
location can be identical. To avoid confusion, mapsets should be
different.

> 2- Shall I apply Geometric Correction procedure before Orthorectification?

No, it would introduce more errors.

Markus M