Triangulation doesn´t work well

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allorens@intercontrol.es
MOHID User
Posts: 27
Joined: Thu Jan 01, 1970 00:00

Triangulation doesn´t work well

Postby allorens@intercontrol.es » Mon May 18, 2009 10:31

Hello,

Sorry for asking so many questions but I'm beginning with this.

I'm trying to get my bathymetry with MOHID GIS but I'm in trouble because I have the same .xyz points:

<begin_xyz>
731868.718 4388516.466 -99.
731633.616 4389977.947 -99.
732182.187 4390917.471 -99.
732051.575 4393292.378 -99.
732835.247 4395432.404 -99.
732368.718 4388516.466 -99.
732133.616 4389977.947 -99.
732682.187 4390917.471 -99.
732551.575 4393292.378 -99.
733335.247 4395432.404 -99.
734368.718 4388516.466 1.
734133.616 4389977.947 1.
734682.187 4390917.471 1.
734551.575 4393292.378 1.
735335.247 4395432.404 1.
735368.718 4388516.466 2.
735133.616 4389977.947 2.
735682.187 4390917.471 2.
735551.575 4393292.378 2.
736335.247 4395432.404 2.
736368.718 4388516.466 3.
736133.616 4389977.947 3.
736682.187 4390917.471 3.
736551.575 4393292.378 3.
737335.247 4395432.404 3.
<end_xyz>
My coastline polygon is (I've done it closed, should it be like that?):

<beginpolygon>
733368.718 4388516.466 0.
733133.616 4389977.947 0.
733682.187 4390917.471 0.
733551.575 4393292.378 0.
734335.247 4395432.404 0.
730863.654 4395426.025 0.
730863.654 4388516.466 0.
<endpolygon>

I try to create the digital terrain, but when it interpolates it changes from the bathymetry 1 to the values in the coast line (and it says that the values in the middle, which should be sea, are negative).

What can I do to get a correct digital terrain?

acanas.maretec@taguspark.pt
MOHID Advanced user
Posts: 103
Joined: Thu Jan 01, 1970 00:00
Location: Instituto Superior Técnico - Technical University of Lisbon

RE: Triangulation doesn´t work well

Postby acanas.maretec@taguspark.pt » Thu May 21, 2009 15:09

Hi,

The polygons have to be closed. This means that the first and last points of polygon have to be the same. This appears not to be the case of your polygon.

Concerning the xyz points it is usual to specify only the bathymetry, the land elevations are not required, since if the land area is included in the land polygon these elevations are not considered by DigitalTerrainCreator in MOHID GIS.

Please let me know if this solved your problem.

Best regards,

Angela


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