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Questions tagged [gis]

A Geographic Information System (GIS) captures, stores, analyzes, manages, and presents data that are linked to location(s). The GIS Stack Exchange should be considered for questions with this tag.

According to Wikipedia:

A geographic information system (GIS), geographical information system, or geospatial information system is any system that captures, stores, analyzes, manages, and presents data that are linked to location(s). In the simplest terms, GIS is the merging of cartography, statistical analysis, and database technology.

There is a Stack Exchange site devoted to Geographic Information Systems.

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How to look up elevation data by lat/lng

I am planning an app that will need the ability to look up the elevation of geographic points by lat/lng. Ideally I would like something that would work worldwide, but US-only would also suffice. I have looked at using the USGS Elevation Query Web…
Bryan
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R: creating a map of selected Canadian provinces and U.S. states

I am attempting to create a map of selected Canadian provinces/territories and selected U.S. states. So far the nicest maps appear to be those generated with GADM data: http://www.gadm.org/ However, I have not been able to plot the U.S. and Canada…
Mark Miller
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MySQL Postgresql / PostGIS

I have lat/lon coordinates in a 400 million rows partitioned mysql table. The table grows @ 2000 records a minute and old data is flushed every few weeks. I am exploring ways to do spatial analysis of this data as it comes in. Most of the analysis…
Dojo
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General Address Parser for Freeform Text

We have a program that displays map data (think Google Maps, but with much more interactivity and custom layers for our clients). We allow navigation via a set of combo boxes that prefill certain fields with a bunch of data (ie: Country: Canada, the…
Daemonic
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Xarray combine_by_coords return the monotonic global index error

I am trying to combine two spatial xarray datasets using combine_by_coords. These two datasets are two tiles next to each other. So there are overlapping coordinates. In the overlapping regions, the variable values of one of the datasets is nan. I…
Ress
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How to approximate a vector contour from an elevation raster?

I have an elevation map stored as a raster. I'd like to fit a smooth "vector" curve to the contours of constant elevation. In my application, the data are actually geographic elevations, but the problem could be generalized to any function of two…
erickson
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clustermarkers in leaflet providing density information in R

I am wondering if it is possible for clusterMarkers in leaflet to display frequency information instead of the number of markers clustered? I have the following code getColor <- function(my.df) { sapply(my.df$value, function(value) { if(value <=…
JWH2006
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Find point which sum of distances to set of other points is minimal

I have one set (X) of points (not very big let's say 1-20 points) and the second (Y), much larger set of points. I need to choose some point from Y which sum of distances to all points from X is minimal. I came up with an idea that I would treat X…
Pawel Markowski
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Calculate distance to shore or coastline for a vessel

For a dataset of 200M GPS (lon, lat) coordinates of vessels I want to calculate an approximate distance to the nearest land or coastline, as a function called distance_to_shore, that will return the distance and country of that shore. I'm using a…
William Grimes
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Convert Lat/Lon to MGRS

Does anyone know where I could find a library of code for converting Lat/Lon position to Military Grid Reference System (MGRS)? I'm looking for a C# implementation if possible.
SwDevMan81
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OpenLayers 3: "movestart" event on map

OpenLayers3 API has a map.on("moveend") , however I cannot find a movestart. Any one know how I can achieve this? Is there a equivalent event? OpenLayers 2 had a movestart event on map. I am looking an exact parallel in OpenLayers3 Here's a basic…
Shaunak
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How to calculate dice coefficient for measuring accuracy of image segmentation in python

I have an image of land cover and I segmented it using K-means clustering. Now I want to calculate the accuracy of my segmentation algorithm. I read somewhere that dice co-efficient is the substantive evaluation measure. But I am not sure how to…
RachJain
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Query points within a given radius in MySQL

I have created the following MySQL table to store latitude/longitude coordinates along with a name for each point: CREATE TABLE `points` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `name` varchar(128) NOT NULL, `location` point NOT NULL, …
gjb
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Finding coordinates of a point in OpenLayers

How can one get the coordinates of a particular point on a map in OpenLayers?
cuser
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google-map tiles missing alt tag causing lower accessibility score

How can we add blank alt tags to the Google map tiles (generated by v3 api) so that they do not lower our accessibility score? http://berkeley.edu/map/googlemap/
user3124388
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