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1500 questions
18
votes
1 answer
Georeferencing using GDAL?
I have a .tiff image that I am trying to overlay in google earth. For that I require to georeference it first.
The image projection is UTM with NAD83 as datum. I know the lat/long of the four corners of the image.
I am doing the following…
Akd
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18
votes
5 answers
Mapping matrix of origins and destinations in QGIS?
I have a central point on a map, and I have other points in a separate layer (the location of a venue, and the origin cities of the venue visitors). Is there a plugin which would generate output similar to airline destination maps like this;
They…
normis
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18
votes
2 answers
Grid vs TIF vs IMG
Grid, TIF and IMG are three formats of raster files.
In ArcGIS Desktop, apparently there's no difference between them.
What is the difference between these three formats?
user
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18
votes
1 answer
Determining flow path length in QGIS?
I need help with qgis flow path length.
I try to run the program and when I run the program I get a raster with 0 values, as input I'm using filled raster, I don't now if I'm doing something wrong or not but i can´t get any map.
user107192
18
votes
3 answers
How much Water on Earth(USGS) : A Wrong Map representation?
I happened to read a USGS article, How much water is there on, in, and above the Earth? showing a representation of all the water(which includes water from Oceans, Seas,Bays,Ice caps, Glaciers, Permanent Snow and ground water) displayed as a small…
vinayan
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18
votes
1 answer
Returning percentage of area of polygon intersecting another polygon using shapely
Using the shapely library, suppose I have a shp file V and another shp file Z. For each polygon v in V, and for each polygon z in Z, I would like to know what percentage of the area of z falls within (intersects) v.
Dervin Thunk
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18
votes
3 answers
How can EPSG:3857 be in meters?
It is said that unit of measure for EPSG:3857 is the metre.
How it can be, if the range of these coordinates is
Projected bounds:
-20,026,376.39 -20,048,966.10
20,026,376.39 20,048,966.10
(from the same source).
This means approximately a square of…
Dims
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18
votes
1 answer
Change marker size in plot with GeoPandas
I have a geodataframe with points and some associated data. I want to plot it on a map using geopandas and have the size of the points correspond to one of the columns in the geodataframe.
So far I have the following code:
base =…
Juan Francisco Saldarriaga
- 517
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18
votes
1 answer
Why is ellipsoidal distance greater than cartesian distance?
I created some linestring features in EPSG:32632 (WGS 84 / UTM zone 32N) exactly 10 000 m long.
QGIS calculates all line lengths (horizontal, vertical, diagonal) as 10 001.9 m. The measure tool explains "Project CRS transformation is turned on and…
Redoute
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18
votes
6 answers
Show images related to features in QGIS?
Say for example, if there's a point data with old trees, then when you use the identify tool, you can see the photograph of the tree
Or even one level further, the labels displaying these images right away without any clicking needed
I believe the…
Luffydude
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18
votes
3 answers
Displaying properties of GeoJSON in popup on Leaflet?
This is my simple GeoJSON with Leaflet map. I want to display properties as popup but I don't know why it is empty.
Can you tell me my mistake?
A Leaflet map!
Alex
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18
votes
1 answer
How do I build a custom form for entering attributes in QGIS
I've done this many times in ArcGIS and ArcPad but I don't even know where to start building a custom form for data entry in QGIS. I would like to do this for field operations--QGIS would make a good field tool with a little customization
Terry Pavlis
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18
votes
1 answer
How do PostGIS functions handle buffers and external storage?
I see an ever increasing list of new functions in PostGIS, some of which involve GEOS (e.g. ST_ClusterKMeans). Some functions (e.g. those in pgrouting) rely on other libraries (e.g. BGL).
My impression is that many of these underlying libraries…
tinlyx
- 11,057
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18
votes
3 answers
Clustering undirected lines
I'm looking for an efficient way to cluster lines independent of their direction. That means that a line between New York and Los Angeles should be in the same cluster as a line in the other direction between Los Angeles and New York. The start /…
underdark
- 84,148
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18
votes
2 answers
ogr2ogr merge multiple shapefiles: What is the purpose of -nln tag?
The basic script in order to iterate recursively over sub-folders and merge all shapefiles into single one is:
#!/bin/bash
consolidated_file="./consolidated.shp"
for i in $(find . -name '*.shp'); do
if [ ! -f "$consolidated_file" ]; then
…
michael
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