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1500 questions
118
votes
14 answers
What ratio scales do Google Maps zoom levels correspond to?
Can anyone provide me with a link (or some details) on the actual ratio to "zoom level" figures for Google Maps?
e.g. Google Maps Level 13 = 1:20000
mlo55
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118
votes
8 answers
Choosing OpenLayers or Leaflet?
I was debating with one of my collegues on OpenLayers v/s Leaflet. I made a point that OpenLayers is much better API if we wish to build a project, where you need direct connectivity to the Geoserver and PostGIS.
Then I found Open Data Kit, which…
Sam007
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- 69
118
votes
13 answers
Accounting for Colour Blindness when designing maps?
Depending on what you read, 7 to 15% of the general population has some form of colour blindness.
Can this be accounted for in map designs and, if so, how?
matt wilkie
- 28,176
- 35
- 147
- 280
114
votes
23 answers
Converting between KML and shapefile (SHP) format
My users are sending me point data that were digitized using Google Earth.
How can I convert their KML to a shapefile and vice versa?
TroutSlayer
- 1,363
- 2
- 10
- 8
114
votes
7 answers
Differences between DEM, DSM and DTM?
I am listing some of the acronyms used in our work and had to stop to think about whether to list these together or separately:
DEM: Digital Elevation Model
DSM: Digital Surface Model
DTM: Digital Terrain Model
In some circles they seem…
blah238
- 35,793
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- 94
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112
votes
5 answers
Merging multiple vector layers to one layer using QGIS
I've imported several shapefiles which where exported from a Mapinfo .tab. Several .tab-files are imported resulting in 20+ layers.
Afterwards I want to export it to GeoJSON; but I'm reluctant to select each layer and export it manually.
Is there a…
stUrb
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- 8
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- 23
110
votes
12 answers
Installing GDAL with Python on Windows
Can anyone explain how to install GDAL/OGR with Python on Windows?
I have Windows Vista and I have tried following the information on the website and it does not seem to bind the *.exe files for me.
Can someone describe the process, including links…
GuidoS
- 1,174
- 5
- 16
- 32
108
votes
16 answers
Identifying Coordinate System of Shapefile when Unknown?
I have a Shapefile but its coordinate system is Unknown, and there is no *.prj file.
How can I identify it now?
com
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- 41
- 57
107
votes
4 answers
What are the pros and cons of PostGIS geography and geometry types?
My company uses geometry (the_geom) data type for storing geospatial data.
I've recently been acquainted to the concept of geography (the_geog) data type which, as I understand it, stores the SRID along with the geometry.
What are the differences…
Adam Matan
- 6,838
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- 37
- 50
104
votes
12 answers
Self-hosting Mapbox vector tiles
As presented in a talk at FOSS4G Mapbox Studio allows to create Mapbox vector tiles and export them as a .mbtiles file.
The mapbox-gl.js library can be used to dynamically style and render Mapbox vector tiles on client (browser) side.
The missing…
Andreas Bilger
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- 2
- 13
- 11
101
votes
27 answers
Python GDAL package missing header file when installing via pip
I asked this question on Stack Overflow before I realised this site existed. As this site it more appropriate, I'll ask it here too.
I'm trying to install gdal from pip pip install gdal inside a virtual environment (Ubuntu). It fails because it…
Kevin
- 1,111
- 2
- 8
- 3
99
votes
4 answers
Getting coordinates from geometry in PostGIS
This line:
SELECT geom
FROM myLayer.geom
will return a hex value.
How would I get decimal values, which is a human-readable coordination?
Kourosh
- 1,299
- 1
- 12
- 13
96
votes
8 answers
Finding minimum-area-rectangle for given points?
As you see in the figure, the question is:
How to find the minimum-area-rectangle (MAR) fitted on the given points?
and a supporting question is:
Is there any analytical solution for the problem?
(A development of the question will be to fit…
Developer
- 3,387
- 4
- 29
- 34
95
votes
5 answers
Renaming attributes/fields in shapefile attribute table using QGIS
I would like to rename some fields in my attribute table:
Like rename "XRF_N3"in something else. It seems quite a easy issue but I don't find any information about how can I do that.
G M
- 2,068
- 2
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93
votes
10 answers
Converting projected coordinates to lat/lon using Python
This site returns
Point:
X: -11705274.6374
Y: 4826473.6922
when you search with the first key value of 000090, as an example. I assume that this is a spatial reference.
I am looking for instructions, or examples, of how to convert this to latitude…
Vincent
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- 6