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Nível DEM: A referência espacial não possui unidade z

xiaoliDong

<\/HEAD>Estou usando a ferramenta ArcHydro para ArcGIS 10. Quando eu estava executando a função "Level DEM", sempre aparece este erro dizendo "Level DEM: Spatial reference does not have z unit". Alguém mais tem o mesmo problema? Alguém poderia, por favor, me ajudar a resolver esse problema? Existe uma maneira de adicionar a unidade z aos dados raster de entrada? <\/SPAN>

Muito obrigado desde já.<\/SPAN><\/BODY><\/HTML>

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curtvprice

Christine, is there a way to do this from Python? This is why I was dismayed it apparently isn't supported in the SpatialReference object even though it seemed like it should be.

AxelThomas

Christine,

I am having the same trouble: any modifications in the adf.prj-file are not recognized by ArcHydro. My raster coordinate system is a national reference system without a Z coordinate system. Consequently the Spatial Reference Properties window does only show a XY Coordinate System tab - there are no existing Z-coordinate systems to modify according to your post. How do I add a new one?

Thank you very much in advance!

Axel

ChristineDartiguenave

The spatial reference is now read from the auxiliary file (*.aux.xml) associated to the raster. This file contains information on the raster that cannot be stored in the raster itself (e.g. spatial reference in the SRS section).

The old projection file is overwritten based on the content of the auxiliary file – this is why ArcMap will not recognize the changes to the projection file.

You can modify the spatial reference properties and set the z unit in the Z Coordinate System tab in the Spatial Reference Properties window.

You can select an existing Z Coordinate System or create a custom one by right-clicking and existing one and selecting Copy and Modify.

Christine Dartiguenave

Esri Water Resources Team

curtvprice

The WTK describes these parameters. Looks they are not exposed in arcpy.SpatialReference, at least as of 10.2.2.

I was trying to get at them with setZFalseOriginAndUnits (false_z, z_units) using values [0, 100] but that doesn't seem to change the WTK text when exported.

PROJCS['NAD_1983_Albers',
GEOGCS['GCS_North_American_1983',
DATUM['D_North_American_1983',SPHEROID['GRS_1980',6378137.0,298.257222101]],
PRIMEM['Greenwich',0.0], 
UNIT['Degree',0.0174532925199433]],
PROJECTION['Albers'],
PARAMETER['False_Easting',0.0],
PARAMETER['False_Northing',0.0],
PARAMETER['central_meridian',-96.0],
PARAMETER['Standard_Parallel_1',29.5],
PARAMETER['Standard_Parallel_2',45.5],
PARAMETER['latitude_of_origin',23.0],
UNIT['Meter',1.0]],
VERTCS['Unknown VCS',VDATUM['Unknown'],
PARAMETER['Vertical_Shift',0.0],
PARAMETER['Direction',1.0],
UNIT['User_Defined_Unit',0.01]];
-16901100 -6972200 266467840.990852;-100000 100;-100000 10000;0.001;0.1;0.001;IsHighPrecision

ChristineDartiguenave

One way of doing this is to edit the projection file associated to the input grid.

- Open the prj file associated to the grid (prj.adf) in a text editor.
- Set the parameters Units to the desired value (e.g. FEET, METERS) for the ground unit if not set.
- Set the parameters Zunits to the desired value for the z-unit. This parameter is set to NO if the z-unit is not explicitly defined: in that case the z-unit is assumed to be the same as the ground unit.

The zunits parameter may be set using a unit name (e.g. METERS, FEET) or a number in the projection file: this number represents the number of zunits that are needed to equal one meter (not one ground unit). For example, for a ground unit in meters, a z-unit in centimeter is defined as:

Units METERS
Zunits 100
as there are 100 cm in 1m.

For a ground unit in feet, a z-unit in centimeter is defined as:
Units FEET
Zunits 100
as there are 100 cm in 1m.

Christine Dartiguenave
Esri Water Resources Team

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