8
votes
3answers
732 views
What is the right solution (and map projection) to compute distances between points located all over the World?
After my study on map projection I realized that it is very difficult to choose a projection that allows to compute simultaneously the distances between a great deal of points if these points are ...
8
votes
2answers
629 views
7
votes
3answers
1k views
how to find 20 closest points efficiently
Say I want to find 20 closest business near me.
My table structure is like this:
BusinessID varchar(250) utf8_unicode_ci No None Browse distinct values Change Drop ...
7
votes
2answers
2k views
Issues with large datasets
I am trying to run an Intersect process in arcgis 10 sp 3 with 2 file sets (aspect and slope) from up to a 1m DEM across an area of 65,000sq km. The aspect has 9,930,384 records and the slope has ...
6
votes
3answers
649 views
How can i split by attribute in ArcGIS 10?
I'd like to split a single shapefile to multiple shapefile by attribute. I found ET Geowizard to do this but it's not free . I arcscripts.esri.com i found a tool named "SplitLayerByAttributes" but it ...
6
votes
3answers
727 views
How to read Greek fonts (ISO-8859-7) in shapefile attributes within QGIS 1.8.0?
I'd like to ask whether there is a way to read greek fonts in a shapefile's attribute table within QGIS 1.8.0.
5
votes
3answers
2k views
Remove spatially duplicate features using ModelBuilder
I am creating a model to remove features which are duplicated within a polygon feature class. Most of the features are duplicated once, but about a quarter have up to three or four exact copies. I do ...
5
votes
2answers
2k views
Rotating a vector layer in QGIS with qgsAffine (or other method)?
I would like to rotate a set of vector points in QGIS an arbitrary number of degrees around a central point (or arbitrary point).
This is similar to a recent question about creating a regular grid; ...
4
votes
8answers
5k views
How to convert KML to shapefile without losing attributes?
I'm new to QGIS and all geoinformation itself but have to work on some difficult stuff.
I have a KML file with hundreds of points. To each point there is information, such as Name, Power, Age (it's a ...
4
votes
4answers
1k views
Calculate distance of point from an arc/polyline
Using Postgres/PostGIS, I am trying to query the database for the closest arc to a particular GPS point. Each Arc is made up of two nodes that are GPS points on a map. Is there a way I could query ...
3
votes
2answers
2k views
Extract by Attribute Using ModelBuilder, With User Input
Using ModelBuilder, I want to create a tool that will let a user choose the value or values that will be used to extract a shapefile.
I have a parcel layer with a "Parcel_Type" field. I want the user ...
2
votes
4answers
981 views
List of Map Service Software
I am curious as to what GIS server software is out there. I have used a few different ones and am building a list of them. If you know of any others please mention it below because I would like to ...
7
votes
2answers
1k views
Distance between lat/long points
I am attempting to calculate the distance between two latitude/longitude points. I have a piece of code that mostly works that I yanked from this post but I do not really understand how it works.
...
6
votes
4answers
1k views
How to georeference a vector layer with control points?
I have a non-georeferenced vector layer that I need to be georeferenced. With raster layers the task is easy and straightforward, but I have no idea what should I do with my vector layer. I have a few ...
6
votes
1answer
773 views
How to create a style file for QGIS from a plain text file?
Using QGIS 1.7.
I have a plain text file, which lists 115 rgb values against a map code for a geological map. Viz.:
$ head gsv1Msymbology.txt
MAPCODE RED GREEN BLUE
Oc 143 255 255
WAT 255 255 255
...
6
votes
2answers
2k views
Is it possible to reproject spatial data using SQL Server?
SQL Server takes an SRID when creating spatial data, but is it possible to retrieve an object as a different spheroid?
For example, let's say I have a bunch of spatial polygons using SRID 4258, but ...
5
votes
2answers
641 views
How to add links to PDFs in a Shapefile?
I have a problem. I want an attribute in a shape file named "Link" to add. The works are all fine. But then I would like to add a link in my directory. This link accesses a PDF. Now, this PDF is not ...
4
votes
3answers
576 views
I exported a DXF from QGIS, but it won't open in AutoCAD
I'm new in QGIS and here is my problem:
I exported a DXf from QGIS by right-clicking on the layer. Then tried to open in AutoCAD 2000.
That did not work. AutoCAD gave a failure-message:
Unknown ...
3
votes
2answers
4k views
Display a WFS layer with OpenLayers
Good Morning!
I have some troubles displaying a WFS layer with OpenLayers and hope someone here can give me a hint. Before moving on, I precise that I have already checked other posts, like here and ...
1
vote
2answers
592 views
Why should we use a proxy script for Apache, Geoserver, OpenLayers?
I can't understand why we use proxy( OpenLayers.ProxyHost)for WMSGetFeatureInfo request in open layer.
I am using open layer 2.10 ,apache-tomcat-6.0.35 and geoserver.
Why we use proxy?
How should ...
8
votes
1answer
1k views
How to convert .shp into .gpx using QGIS?
I'm newbie using QGIS. I would like to convert .shp into .gpx. So, using Qgis, I open my shapefile and I tried to "save as" gpx but it gives an OGR error:
creation of field ObjectId failed (OGR ...
7
votes
3answers
309 views
Is there a st_buffer inverse function, that returns a width estimation?
When you supply a geometry g1 and a width w to the standard OGC function ST_Buffer,
it returns a new geometry g2,
g2 = ST_Buffer(g1,w)
This question is about the inverse: a function where you ...
7
votes
6answers
2k views
Lines to Polygons
I have failed to find the "name" of the algorithm that would allow one to convert lines to polygons. Since this issues crosses GIS and the fields of computational geometry and computer science. I am ...
6
votes
1answer
262 views
Where are the Expression-based Labeling options in QGIS?
I have imported a layer into my map to show the location of towns/cities. However I had to set graduated styling so that only cities over a certain population show.
I now want to label the ones that ...
5
votes
3answers
5k 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 ...
5
votes
2answers
1k views
How to use ArcObjects to choose GeoTransformation?
I’m currently building a Desktop add-in tool with ArcObjects that:
Asks a user to select a feature class
Reprojects the feature class to Web Mercator
Executes some geoprocessing
The initial ...
5
votes
2answers
4k views
ArcGIS: In the Legend, show legend items that are only displayed on the map
Using ArcGIS, is there a way for the legend, to only show the subitems that are displayed on the map?
4
votes
2answers
1k views
How to add automate values to attribute field?
I have parcel, Buildings layers, without any information attribute table, and i want to replace "NULL" values with numbers form 1 to 2000, in "Parcel ID", or "Building ID" field
thank you.
3
votes
1answer
226 views
Raster incorrectly reprojected to OSGB(27700)
Ubuntu 12.04, QGIS 1.8.0, GDAL/OGR 1.7.3, GEOS 3.2.2
Open a Spatialite db with OS Mastermap poly layer (EPSG:27700);
Add OpenLayers Plugin (1.0) from QGIS offical repository;
Add a Google Satellite ...
3
votes
1answer
381 views
ArcObjects + comtypes at 10.1
Has anyone played around with using ArcObjects in Python at version 10.1?
I am having all sorts of problems, such as TypeErrors when wrapping the ESRI OLB modules and AttributeErrors when attempting ...
3
votes
1answer
429 views
ArcGIS: How do you get an annotation layer working inside a group layer?
How do you get an annotation layer working inside a group layer? When I try I get the error message "error adding element".
I have a project that requires several annotation layer to be organised ...
2
votes
1answer
239 views
How to style a layer from console?
I am new to the QGIS python console.
I am trying to load a raster layer from the console, set the crs and a specific style from a qml file.
layerPath = os.path.join(raster_dir,raster_name)
fileInfo = ...
2
votes
3answers
2k views
Problem with ArcToolbox tools
I work with ArcGIS 9.3. When I try to run any ArcToolbox tool I receive the message:
Window Internet Explorer (Title of the Window)
"One or more ActiveX controls could not be displayed because ...
1
vote
3answers
379 views
Where can I find the finest granularity of 2010 US census population information?
I am writing a re-districting application where I want to be able to create US voting districts based on geographic coordinate population data. In a perfect world, I would have the population for each ...
1
vote
1answer
668 views
How to verify a PostGIS installation on OS X?
I am trying to set up GeoDjango and installing PostGIS on my mac and when I am trying to
./configure
I am getting this error
checking PostgreSQL version... PostgreSQL 8.4.9
checking libpq-fe.h ...
1
vote
1answer
639 views
How do I calculate ECEF X,Y,Z velocities for GPS if I have no satellites
I'm attempting to simulate a GPS message where know variables are starting location, ending location, speed (m/s), and a bearing (0 - 359 degrees). How can I calculate the ECEF X, Y, Z velocities ...
34
votes
10answers
3k views
What is the most useful spatial R trick?
R is becoming pretty strong tool for handling and analyzing spatial data. I learned some useful things through questions like these at SO and thought it might be useful to have something simmilar, but ...
53
votes
13answers
3k views
How much math does a GIS Analyst need to know?
For someone studying to pursue a career as a GIS Analyst, what math courses should he/she take?
Update
Here's a long list of free Math courses from MIT to serve as a frame of reference.
Which are ...
26
votes
7answers
2k views
31
votes
9answers
2k views
Alternatives to using Arcpy
I seem to use ESRI's Arcpy site package for virtually all of my python geoprocessing. To ESRI's credit, these are an incredible suite of tools that can help accomplish a great deal. However, I would ...
17
votes
8answers
641 views
What are some resources for learning Python and arcpy?
I would like to learn arcpy, but I do not know quite where to begin. Does anyone have any good advice on where I should start to learn arcpy?
35
votes
4answers
1k views
What are the FOSS equivalents to these ArcGIS products?
I'm a long-term user of ESRI software, and I now have a need to use free and open source software.
I've been reading about Open Layers, PostgreSQL, PostGIS, GeoServer and MapServer but I can't find ...
14
votes
9answers
1k views
What are the Python tools/modules/add-ins crucial in GIS?
With ArcGIS 10, Python has become the de-facto scripting language for ESRI. While leading Open source software like QGIS, GeoServer, PostGIS all supports Python. Thus it became important to know/learn ...
29
votes
8answers
8k views
QGIS and gvSIG comparison
Many debutant GIS users are asking me which one is better QGIS or gvSIG. Since I use Qgis and I don't have any experience in gvSIG, I aways say that both are very nice softwares and the chose is a ...
19
votes
7answers
6k views
Options for displaying PostGIS vectors in OpenLayers
I am very new to web-mapping, so this question may be a little misguided.
I want to have a very simple web interface using OpenLayers (or even Google Maps if that will be easier) which can display a ...
14
votes
3answers
2k views
How to put GeoServer layers behind authentication?
I want to publish map layers using OpenLayers and GeoServer. While this is easy enough to set up, I'm a bit lost when it comes to authentication possibilities. What I want is to create different users ...
12
votes
8answers
364 views
List of US government free GIS data online
The US government publishes a plethora of useful, high-quality GIS data sources online.
The data includes:
Municipal and international boundaries
Classified points of interest
Geographic maps
...
23
votes
6answers
2k views
Options for ArcGIS Desktop SpatiaLite support?
SpatiaLite is playing an increasing role in my organization. As it stands now, using SpatiaLite alongside ArcGIS Desktop requires an amount of importing and exporting of data that isn't always ...
21
votes
1answer
2k views
How to find the center of geometry of an object?
Well it might be a simple question. Given a set of 2D or 3D points, the question is:
How to find the center of geometry of an object?
According to the following figure, the center of geometry ...
18
votes
6answers
569 views
Machine Learning Algorithms for Land Classification
I am interested in learning what software exists for land classification using machine learning algorithms (e.g. k-NN, Random Forest, decision trees, etc.) I am aware of the randomForest package in R ...
