Segment editor - create polygon map, satellite image as reference

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Segment editor - create polygon map, satellite image as reference

Peter Brakels
Hi, i want to draw some forest boundaries on a satellite image (rastermap) to create a polygon. Any suggestions on how to preform this operation. There is no sign of the segment editor, i am sorry I can't find it and I have no clue what to do with a blank segment map, since I need the satellite image as a reference/basemap.
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Re: Segment editor - create polygon map, satellite image as reference

Bas Retsios
Hi!

Use ILWIS 3.7.x or older to digitize. We haven't yet ported the
digitizer code to ILWIS 3.8.x

Steps:
1. Open the raster image. Use a projected coordinate system if possible
(as opposed to LatLon degrees). An easy way to check if the image uses a
projected coordinate system, is by reading out the coordinates that are
displayed at the bottom-right of the Map Window, while moving the mouse
over the map. If you only see pixel positions, then the image is not
even georeferenced. If you see pixel positions and Lat/Lon degrees, it
is georeferenced, but not projected. If you see all 3 coordinate pairs
(pixel positions, projected coordinates in meters, and latlon
coordinates in degrees), then it is projected, which is the preferred
situation for digitizing.

2. In the menu of the Map Window, choose File->Create Segment Map.
Change the domain to whatever you need the values of the segments to be
(e.g. VALUE). Confirm that the boundaries make sense. Then click OK.

3. Digitize the segment map. If you haven't used ILWIS to digitize, see
the ILWIS help on how this works. If digitizing refuses to enter any
points when you are in "Insert Mode", but beeps instead, quite likely
you are dealing with an ungeoreferenced or unprojected image (see step
1). If you do not want to project it, try to extend the lat/lon
boundaries in step 2, to something different than 0, 0, 0, 0. The "beep"
is because the digitizer complains that you are digitizing outside the
specified boundaries.

Bas Retsios
ILWIS team.

On 26/5/2014 07:21, Peter Brakels wrote:

> Hi, i want to draw some forest boundaries on a satellite image (rastermap) to
> create a polygon. Any suggestions on how to preform this operation. There is
> no sign of the segment editor, i am sorry I can't find it and I have no clue
> what to do with a blank segment map, since I need the satellite image as a
> reference/basemap.
>
>
>
> --
> View this message in context: http://ilwis.forum.52north.org/Segment-editor-create-polygon-map-satellite-image-as-reference-tp4025687.html
> Sent from the 52° North - ILWIS Community Forum mailing list archive at Nabble.com.
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