22
votes
1answer
8k views

Trilateration algorithm for n amount of points

I need to find algorithm that can calculate centroid A (aka gravity center, geometric center, center of mass) from the figure where circles T1,T2,T3,T4,T5,..,Tn intersect AND length of line R from ...
15
votes
1answer
2k views

How to draw perpendicular lines in QGIS?

I have a situation like this: What I need to do is to connect each point to every line that is at most, let's say 200 m, away from the point. In other words, I need to draw a perpendicular line ...
14
votes
10answers
10k views

How to convert ArcGIS Server JSON to GeoJSON?

I'm creating a web map using Leaflet, and I want to be able to grab feature layers from our ArcServer. I have successfully been able to retrieve a feature class as JSON, but Esri's JSON objects don't ...
13
votes
4answers
1k views

How can I generate irregular grid containing minimum n points?

Given a large (~ 1 million) sample of unevenly distributed points - is it possible to generate irregular grid (in size, but could also be irregular in shape if that is possible?) that will contain ...
18
votes
4answers
6k views

Separate polygons based on intersection using PostGIS

I have a PostGIS table of polygons where some intersect with one another. This is what I'm trying to do: For a given polygon selected by id, give me all of the polygons that intersect. Basically, ...
34
votes
4answers
9k views

LatLon or LonLat, what's the “right” way to display coordinates and inputs?

I'm trying to get a sense if this is an issue for others or every input/output should be labeled so user is not confused and just go with it? I think almost everyone pronounces it as "LatLon". Who ...
19
votes
10answers
3k views

Discontinuous or Interrupted map projections?

Do any of the current open source GIS softwares support discontinous projection systems? E.g. sinusoidal, dymaxion, butterfly, etc? If not, are there any affordable commercial ones that do (affordable ...
22
votes
1answer
16k views

How to install a QGIS plugin when offline?

Due to various IT policies at my workplace, QGIS is installed on a machine that is not connected to the internet. I wish to install a couple of QGIS plugins on this system. I have downloaded the ...
10
votes
3answers
4k views

Land Cover Feature Extraction from Satellite Imagery

I'm interested in a low-cost or open source solution for creating land cover GIS layers that utilize both spectral and textural extraction algorithms. I have used PCI Geomatica, ENVI, and Feature ...
12
votes
2answers
2k views

How to count and rasterize polygon overlaps in ArcGIS Desktop?

How do you take a vector layer with overlapping polygons and turn it into a raster where each cell counts the number of polygons containing that cell? We are looking at polygons of fire burn areas ...
18
votes
3answers
5k views

How to call gdal_translate from Python code?

Is it possible to use some gdal API to call gdal_translate from Python code? I do not mean simply executing the gdal_translate.py from the file system, but rather call it somehow in code so I do not ...
17
votes
9answers
3k views

GIS data for fast food industry

I am working a small project related to fast food industry. I am trying find GIS data for fast food chains like subway, MC Donald's, Arby's, etc in state of Ohio. Basically, I am looking for point ...
17
votes
9answers
9k views

How can I convert an excel file with x, y columns to a shapefile?

How can I convert an excel file with x, y columns to a point shapefile? There are some somewhat optional requirements in addition to the correct creation of a shapefile: Column types (as per ...
9
votes
4answers
8k views

How to change feature class and field aliases in bulk?

I have over a hundred FCs, each with 10 or 20 attributes to add or change the aliases for, two or more times a year. Needless to say, this is not something I'm going to grunt my way through. How can I ...
15
votes
4answers
1k views

algorithm to place maximum number of points within constrained area at a minimum spacing

I have a polygon layer that describes a constraint; I wish to add points within this area. I want to add as many points as possible, but they must have a minimum spacing between them. Is it possible ...
11
votes
4answers
3k views

Is it possible to export GeoPDF from QGIS?

Is there any plugin for QGIS which would help me in exporting the map document as a GeoPDF ?
9
votes
4answers
2k views

Elevation profile 10 km each side of a line

How can I get an elevation profile for a band of terrain? The highest elevation within 10 km (on each side of the defined line) should be taken into account. I hope my question is clear. Thank you ...
8
votes
3answers
876 views

How to apply the four colors theorem in a polygon map in ArcGIS/ArcToolBox automatcally?

I need to apply the four colors theorem in a polygonal shape in a way that I do not need to choose manually each color to put in each region. I wish to knows if there is any extension, plug-in, script ...
8
votes
7answers
5k views

Extract raster values at points

How can I extract values from a raster by points. I prefer not in Arcgis. I prefer in Qgis or Mapwindow or other open source gis.
7
votes
2answers
2k views

How to build an artificial 'dam' across a river?

I have a DEM. Created all files related to watershed including accumulation, direction, streams etc... I'm stuck creating a dam. I request you to please let me know how to build an artificial 'dam' ...
5
votes
5answers
3k views

How to calculate distances in a point sequence?

I'm looking for help calculating the distance between a sequence of points that are in a single Shapefile in QGIS. Below is what my data look like and a blank distance column I've added to show how ...
4
votes
2answers
845 views

Is Shooting Star broken in PGRouting 1.05?

I'm using pgrouting DLL 1.05 with postgresql 9.1. All required function installed. Astar and Dijkstra work fine with sample data but "SHOOTING STAR" is not considering "reverse_cost". Also if i try ...
11
votes
3answers
7k views

Google Maps layer copyright popup every time map updated / user input

I have used a Google Maps hybrid layer in Openlayers in my HTML5 iOS app for months now and it worked perfectly. Just recently they changed something because the 'Map data...' line at the bottom looks ...
7
votes
2answers
7k views

ECW for QGIS 1.8 in Ubuntu 12.04

I have followed various online help guides on how to make ecw for QGIS 1.8 work in Ubuntu 12.04. I had it all working in Ubuntu 10.04 but since migration to 12.04 no such luck. Is there a guide that ...
3
votes
2answers
1k views

Colouring areas between (vector) contours?

Is it possible to colour areas between (vector) contours without making it a DEM first? Joshdoe seems to have done so in Create filled contour map with GRASS but does not say how.
2
votes
1answer
1k views

GDAL2Tiles: MapTiles from BSB/KAP are Switched

As an example I have a BSB file from NOAA which is a navigational map. The map has a SRS of WGS84 and a Mercator projection. I initially translate the file from BSB format to GTiff format using the ...
11
votes
2answers
10k views

How to reproject a vector layer in QGIS?

I have some shape file which is in UTM. I wanted them to convert to Decimal Degrees in QGIS. Thanks.
11
votes
3answers
16k views

How to convert a vector layer to raster?

In qgis in the raster menu there is an item "convert vector to raster". This behaves strangely - I do not understand how it is supposed to work. I can select a vector file, an attribute and an ...
2
votes
3answers
1k views

How to auto increment a field in a feature class?

So I'm relatively new to ArcGIS and ArcCatalog. I have created a field name of PROJECTID in a feature class in a Personal Geodatabase. The data type is TEXT. This will be a ten digit ID. The first ...
14
votes
2answers
3k views

Using Geodesic Measurements for Circle Radii?

I am currently developing an OpenLayers mapping site. Measurements can be made using a line tool, and an area tool. Both of these are currently set to calculate geodesic measurements as outlined in ...
2
votes
3answers
344 views

How to determine bare earth from unclassified LAS file

I have data in LAS format with RGB values created from Aerial photogrammetry using a UAV. I am trying to find a solution to extract the bare earth to create my DTM from the DSM. I have tried SAGA, ...
1
vote
2answers
276 views

How to define Subroutines and functions?

I am working in VBA. My error is sub and function are not defined. Here is my code: Private Sub CreateMap(cboDistrict As String) Dim mapDocument As New mapDocument If ...
45
votes
13answers
13k views

Resources for learning Python programming with generic GIS goals in mind?

In your opinion, what is the best book/site to learn Python with GIS goals in mind? By "best", I mean: not very long (book) easy to understand (book/site) good practical examples (book/site) For ...
40
votes
7answers
4k views

Best practices for PostGIS production environments?

What PostGIS documentation have you come across that has been helpful when tuning PostGIS for a production environment? I would like to get together with my DBA to setup a Postgresql/PostGIS ...
34
votes
2answers
4k views

Acquiring ArcGIS-like speed in Postgis

I have been using Postgis 2.0 for 3/4 of a year now and while I really enjoy using it, excessive query processing time has rendered it basically unusable for my use case. I tend to do heavy ...
35
votes
7answers
6k views

How can I effectively debug arcpy Python scripts?

I have written many Python scripts using arcpy in ArcGIS 10, and so far my only means of debugging is restricted to printing messages to the geoprocessing results window using arcpy.AddMessage(). Are ...
20
votes
9answers
6k views

How do I develop my GIS programming skills?

I would like to develop my GIS programming skills, where do I start? People say learn C++ or Python but where can I learn this in a geographic context? Tutorials or anything would be very helpful, as ...
22
votes
3answers
7k views

Simple thematic mapping of shapefile using Python?

I wish to visualize geographical data in Python, without using ArcGIS/ArcPy, and make a map. On the internet I found how to make a thematic map using Python: Here is some code that I tried: ...
25
votes
9answers
14k views

How to connect to PostGIS database from ArcMap?

How can I connect to a PostGIS database from ArcMap? Solutions for ArcGIS 9.3, 10.0 and later are acceptable. Ideally, I would like to be able to perform spatially enabled queries and receive the ...
21
votes
3answers
14k views

How to convert ArcGIS .mxd file to QGIS .qgs file?

I recently tried to use QGIS and I wondered if you can convert a draft ArcGIS map (*.mxd file) into a QGIS project (*.qgs file). This would avoid thematize the entire project.
19
votes
9answers
12k views

Bulk Geocode 20 million records

Are there any free or reasonably priced databases for the US which can be searched and return latitude and longitude information?
19
votes
4answers
2k views

How do GIS web apps work?

I am completely new to GIS and therefore have questions regarding how the GIS Web development should be made, because the entire concept still confuses me. So, imagine I have a map. And by this, i ...
21
votes
5answers
3k views

How to create regular point grid inside a polygon in Postgis?

How to create, inside a polygon, a regular grid of point spaced x,y in postgis? Like the example:
15
votes
2answers
3k views

Calculate distortion outside a UTM zone

One of my colleagues is working with data that is spread across two UTM zone. The majority of the data is in one zone, with a few outliers in another zone. He would like to know what the area ...
9
votes
4answers
3k views

Connecting line features and determining the length of the longest line

I have a line feature (see image) representing a river that I created using the Stream_to_Feature tool. The attribute table contains several records representing different lines - the problem is the ...
18
votes
2answers
6k views

How can I convert data in the form of lat, lon, value into a raster file using R?

I have a data set of values over a km grid in the continental U.S. The columns are "latitude", "longitude", and "observation", e.g.: "lat" "lon" "yield" 25.567 -120.347 3.6 25.832 ...
8
votes
1answer
1k views

Creating table containing all filenames (and possibly metadata) in File Geodatabase?

I need to create a metadata-table for all files in a File Geodatabase or Spatial Database. It would be awesome if it were possible to automatically be updated with new filenames, and possibly even ...
8
votes
6answers
3k views

Get a point on a polyline from end points given distance along poly line

I have start point and end point of a polyline. How can I get a point on that polyline from end points specified by the given distance. How can I get this by using arcpy provided that this script ...
20
votes
3answers
2k views

Packing Polygons within polygon

I have a Boolean raster. In the grey areas of the raster I would like to fit a given size polygon within a contiguous extent. Basically, I have an irregular polygon, and i would like to "fit" a ...
8
votes
2answers
583 views

Creating summary table of symbology of all datasets in multiple MXDs?

This is related to the following Retain ESRI symbology in Mapinfo TAB . As an initial step (in arcpy) I want to access the symbology of all the datasets and create a document which has the details of ...

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