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1500 questions
18
votes
7 answers

Sources of realtime spatial data

I'm trying to set up a demo that serves up live spatial data, but am having trouble finding any suitable example data sources. Ideally I'm looking for something that updates every few seconds; either with a new position or maybe a fixed position but…
Mark Ireland
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2 answers

Changing color of raster images based on their data values - gdal

Let's say I have 1 band raster images with Gray Color Interpretation and I want to change their color based on their data values. Data values -1, will be Blue, -0.5 will be Light Blue, 0 will be Yellow, 0.5 will be Orange and 1 will be Red. If the…
lovelyvm
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18
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4 answers

Using GIS tools for non-geographical problems

Many other fields have visual/"spatial" problems that can potentially be solved with GIS tools. I know I've used GIS tools for the odd non-geographical task and was wondering how much this happens and if anyone had any good examples of where this…
GIS-Jonathan
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18
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4 answers

Changing mouse wheel zoom settings in QGIS?

I'm having a problem with the mouse wheel zoom setting on my macbook trackpad. The zoom occurs far too quickly for any level of precision. I noted this comment in the dev log: 2004-08-14 [gsherman] 0.4.0devel9 Added mouse wheel zoom. Moving wheel…
Ben
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18
votes
3 answers

Zigzag Line Symbol in QGIS

I'm looking for a zigzag line symbol in QGIS. I have tried creating a marker line using a simple triangle marker (^) and adjusting the size of the marker and the marker placement interval until the triangles touched each other and appeared to make a…
Joanna McMillan
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18
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12 answers

How do you memorize the meaning of longitude and latitude?

Longitude and latitude are concepts I usually don't need to remember them. However I sometimes suddenly need to learn their meaning for a period of time because I am using them. Is there an aide-memoire(memory - aid) to finally remember their…
Raffael
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18
votes
4 answers

Are ArcGIS *.lyr and *.mxd data format specs published?

Are the binary formats of *.lyr and *.mxd files published?
Scott Wisniewski
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18
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1 answer

Choosing projected coordinate system for mapping all US states?

I'm on a project requires integrating data for all states in the US. It means I have two roadway datasets and I'm going to assign the attributes of roadways in one dataset to the same roadways in the other dataset (similar to spatial join). Each…
12B01
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17
votes
2 answers

Creating Shapely LineString from two Points

If have two points, from which I want to create a straight LineString object: from shapely.geometry import Point, LineString A = Point(0,0) B = Point(1,1) The Shapely manual for LineString states: A sequence of Point instances is not a valid…
ojdo
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17
votes
7 answers

Free tool to simplify parcel shapefiles?

Is there any tool available which let's me run millions of parcel shapefiles and simplify them?
NetConstructor.com
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17
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6 answers

What cartographic line symbol could make a coastline represent water like this old map?

I live in a coastal area with lots of islands. Sometimes with a black and white map it's hard to distinguish land from sea. So I'm trying to replicate this old map's style. I'm trying to do this in QGIS but if it's easier in ArcGIS I'd be happy to…
jfact0ry
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17
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1 answer

Query OSM for all beaches facing west? - QGIS preferred

I want to identify all beaches on this planet (or a given subset of it) that are facing westwards (+/- 20-30 degrees). My idea is to use OSM as the data source. Extracting all polygons that have the tag "natural=beach" gives me a dataset / shapefile…
jdoe
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17
votes
2 answers

Getting "Points of LinearRing do not form a closed linestring"

I downloaded the data provided here as KML, exported to ESRI Shapefile format, checked it on QGIS and everything looked fine. Upon trying to use the layermapping utility of Geodjango I am getting the error GEOS_ERROR: IllegalArgumentException:…
kuch nahi
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17
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2 answers

GDAL polygonize in python creating blank polygon?

I am having trouble using the Polygonize function in python. The cookbook example for this can be found here. The relevant portion of my code is: sourceRaster = gdal.Open('myraster.tif') band = sourceRaster.GetRasterBand(1) bandArray =…
camdenl
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17
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4 answers

Refreshing imported modules in ArcGIS Python Toolbox?

When using a python toolbox (.pyt) in ArcMap, I'll typically follow a pattern where the .pyt file itself is simply a wrapper to collect input arguments and define the tools themselves. Supporting code is kept in separate unit-testable modules. …
Josh Werts
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