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Spatial reference extent limitations ?

TieshengWu

I would like to get features spatial reference limitations of coordinate x and y by using snippet like:

sr = arcpy.Describe('my feature').spatialReference

dom=sr.domain.split()
xmin=float(dom[0])
ymin=float(dom[1])
xmax=float(dom[2])
ymax=float(dom[3])

...

But it seems don't work. For a WGS84 GCS, the result is xmin=-180, xmax=180, ymin=-90 but ymax=270 rather than 90, and more strange result for a WGS84 PCS. Does sr.domain is not proper for my needs?

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Accepted answers

MelitaKennedy

It's pulling the spatial reference xy domain which is square. The lower left / minimum values are good, but the max values may be blown out to either make the extent square or to make the xy resolution value a reasonable number.

The -400 is to cover data that could be in -360 to 0 longitude range, with a very generous buffer added. We just used the same value for the minimum Y (latitude) value too.

<SPAN class="" style="color: #a67f59; background: rgba(255, 255, 255, 0.5); border: 0px; font-weight: inherit; font-size: 14px;">-</SPAN><SPAN class="" style="color: #990000; border: 0px; font-weight: inherit; font-size: 14px;">400</SPAN> <SPAN class="" style="color: #a67f59; background: rgba(255, 255, 255, 0.5); border: 0px; font-weight: inherit; font-size: 14px;">-</SPAN><SPAN class="" style="color: #990000; border: 0px; font-weight: inherit; font-size: 14px;">400</SPAN> <SPAN class="" style="color: #990000; border: 0px; font-weight: inherit; font-size: 14px;">1000000000</SPAN><SPAN class="" style="color: #999999; border: 0px; font-weight: inherit; font-size: 14px;">;</SPAN><SPAN class="" style="color: #a67f59; background: rgba(255, 255, 255, 0.5); border: 0px; font-weight: inherit; font-size: 14px;">-</SPAN><SPAN class="" style="color: #990000; border: 0px; font-weight: inherit; font-size: 14px;">100000</SPAN> <SPAN class="" style="color: #990000; border: 0px; font-weight: inherit; font-size: 14px;">10000</SPAN><SPAN class="" style="color: #999999; border: 0px; font-weight: inherit; font-size: 14px;">;</SPAN><SPAN class="" style="color: #a67f59; background: rgba(255, 255, 255, 0.5); border: 0px; font-weight: inherit; font-size: 14px;">-</SPAN><SPAN class="" style="color: #990000; border: 0px; font-weight: inherit; font-size: 14px;">100000</SPAN> <SPAN class="" style="color: #990000; border: 0px; font-weight: inherit; font-size: 14px;">10000</SPAN><SPAN class="" style="color: #999999; border: 0px; font-weight: inherit; font-size: 14px;">;</SPAN><SPAN class="" style="color: #990000; border: 0px; font-weight: inherit; font-size: 14px;">8.98315284119522E-09</SPAN><SPAN class="" style="color: #999999; border: 0px; font-weight: inherit; font-size: 14px;">;</SPAN>\
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="" style="color: #990000; border: 0px; font-weight: inherit; font-size: 14px;">0.001</SPAN><SPAN class="" style="color: #999999; border: 0px; font-weight: inherit; font-size: 14px;">;</SPAN><SPAN class="" style="color: #990000; border: 0px; font-weight: inherit; font-size: 14px;">0.001</SPAN><SPAN class="" style="color: #999999; border: 0px; font-weight: inherit; font-size: 14px;">;</SPAN>IsHighPrecision"

These values are (in order):

minimum X, minimum Y, inverse of xy resolution;

minimum Z, inverse of Z resolution;

minimum M, inverse of M resolution;

XY tolerance;

Z tolerance;

M tolerance

True that the spatial reference is high precision versus the original "basic" precision.

The tolerance values are actually not good if the data is using a geographic coordinate system.

Wu Teshieng, you probably want the coordinate system's "projected horizon" but I don't think that's exposed in arcpy. Here's some of the methods in ArcObjects:

https://desktop.arcgis.com/en/arcobjects/latest/net/webframe.htm#iprojectedcoordinatesystem4_getpcshorizon.htm

The PCS horizon but in latitude/longitude. It is not guaranteed to be an inclusive horizon (it might be exclusive to show which part of the world can't be 'seen' in the particular PCS).

https://desktop.arcgis.com/en/arcobjects/latest/net/webframe.htm#iprojectedcoordinatesystem2_gethorizon.htm

All comments

TieshengWu

Yes it's helpful. But in my situation, the spatial reference of the feature is unknown in advance, so I must have a method to get the limit extent and using that in my code to avoid the out of extent error.

JoeBorgione

I am dealing with a similar issue with respect to extents. (See: Spatial Extents ). When I append source data to a (emtpy) target the the extents are sometimes well out of bounds my area of interest. Allegedly, the process of appending re-calculates the extent, and I've had that happen. But, I still get feature classes that have an extent of USA and the Philippines when all the data should reside in one county, in one state of the US.

When you define an empty feature class with a given spatial reference, it is given the extents of 0,0,0,0. Once you add features to the feature class, the extent is supposed to be that of the features themselves...

TieshengWu

Thanks for your responding Joe. My concern is the largest extent limit of any coordinate system, GCS or PCS. The problem arise from a practical problem, that is, when a polygon feature is create using ArcPy, the limit extent of the coordinate system may be exceeded and making the feature invalid.

JoeBorgione

What is your objective? Are you most concerned with the actual Spatial Reference of your data or are you concerned with extent of your data?

If the latter, consider the snippet of code below that returns the XMin/Max YMin/Max of a given feature class (fc):

fc <SPAN class="operator token">=</SPAN> <SPAN class="string token">'YourFeatureClass'</SPAN>
descFC <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>Describe<SPAN class="punctuation token">(</SPAN>fc<SPAN class="punctuation token">)</SPAN>
fc_xmin <SPAN class="operator token">=</SPAN> descFC<SPAN class="punctuation token">.</SPAN>extent<SPAN class="punctuation token">.</SPAN>XMin
fc_ymin <SPAN class="operator token">=</SPAN> descFC<SPAN class="punctuation token">.</SPAN>extent<SPAN class="punctuation token">.</SPAN>YMin
fc_xmax <SPAN class="operator token">=</SPAN> descFC<SPAN class="punctuation token">.</SPAN>extent<SPAN class="punctuation token">.</SPAN>XMax
fc_ymax <SPAN class="operator token">=</SPAN> descFC<SPAN class="punctuation token">.</SPAN>extent<SPAN class="punctuation token">.</SPAN>YMax

<SPAN class="keyword token">print</SPAN> <SPAN class="string token">'Extents of {}, {}, {}, {}, {}'</SPAN><SPAN class="punctuation token">.</SPAN>format<SPAN class="punctuation token">(</SPAN>fc<SPAN class="punctuation token">,</SPAN>fc_xmin<SPAN class="punctuation token">,</SPAN>fc_ymin<SPAN class="punctuation token">,</SPAN>fc_xmax<SPAN class="punctuation token">,</SPAN>fc_ymax<SPAN class="punctuation token">)</SPAN>

‍‍‍‍‍‍‍‍<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

DanPatterson_Retired

Interestingly... if you run the code snippet for a gcs wgs84 from

SpatialReference—ArcPy classes | ArcGIS Desktop

You get some strange results.

Perhaps Melita Kennedy‌ can offer some insight

wkt <SPAN class="operator token">=</SPAN> "GEOGCS<SPAN class="punctuation token">[</SPAN><SPAN class="string token">'GCS_WGS_1984'</SPAN><SPAN class="punctuation token">,</SPAN>DATUM<SPAN class="punctuation token">[</SPAN><SPAN class="string token">'D_WGS_1984'</SPAN><SPAN class="punctuation token">,</SPAN>SPHEROID
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="punctuation token">[</SPAN><SPAN class="string token">'WGS_1984'</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="number token">6378137.0</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="number token">298.257223563</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN>\
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; PRIMEM<SPAN class="punctuation token">[</SPAN><SPAN class="string token">'Greenwich'</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="number token">0.0</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN>UNIT<SPAN class="punctuation token">[</SPAN><SPAN class="string token">'Degree'</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="number token">0.0174532925199433</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN>\
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; VERTCS<SPAN class="punctuation token">[</SPAN><SPAN class="string token">'WGS_1984'</SPAN><SPAN class="punctuation token">,</SPAN>DATUM<SPAN class="punctuation token">[</SPAN><SPAN class="string token">'D_WGS_1984'</SPAN><SPAN class="punctuation token">,</SPAN>SPHEROID
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="punctuation token">[</SPAN><SPAN class="string token">'WGS_1984'</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="number token">6378137.0</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="number token">298.257223563</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN>\
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; PARAMETER<SPAN class="punctuation token">[</SPAN><SPAN class="string token">'Vertical_Shift'</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="number token">0.0</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN>PARAMETER<SPAN class="punctuation token">[</SPAN><SPAN class="string token">'Direction'</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="number token">1.0</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">,</SPAN>UNIT
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="punctuation token">[</SPAN><SPAN class="string token">'Meter'</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="number token">1.0</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">;</SPAN>\
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="operator token">-</SPAN><SPAN class="number token">400</SPAN> <SPAN class="operator token">-</SPAN><SPAN class="number token">400</SPAN> <SPAN class="number token">1000000000</SPAN><SPAN class="punctuation token">;</SPAN><SPAN class="operator token">-</SPAN><SPAN class="number token">100000</SPAN> <SPAN class="number token">10000</SPAN><SPAN class="punctuation token">;</SPAN><SPAN class="operator token">-</SPAN><SPAN class="number token">100000</SPAN> <SPAN class="number token">10000</SPAN><SPAN class="punctuation token">;</SPAN><SPAN class="number token">8.98315284119522E-09</SPAN><SPAN class="punctuation token">;</SPAN>\
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="number token">0.001</SPAN><SPAN class="punctuation token">;</SPAN><SPAN class="number token">0.001</SPAN><SPAN class="punctuation token">;</SPAN>IsHighPrecision"

sr <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>SpatialReference<SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN> sr<SPAN class="punctuation token">.</SPAN>loadFromString<SPAN class="punctuation token">(</SPAN>wkt<SPAN class="punctuation token">)</SPAN>

r<SPAN class="punctuation token">.</SPAN>domain

<SPAN class="string token">'-400 -400 9006799.25474099 9006799.25474099'</SPAN><SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

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