6
votes
1answer
958 views

Difference between Geographic-3D and Geocentric CRS

I'll start with the OGP definitions: Geographic. A coordinate reference system based on a geodetic datum and using an ellipsoidal (including spherical) model of the Earth. This provides an accurate ...
5
votes
1answer
469 views
5
votes
3answers
1k 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 ...
5
votes
2answers
620 views

Identify the latitudinal and longitudinal point directly beneath an object in space

Given the azimuth and altitude / latitude and longitude from the observer to the satellite, how can I accurately find the latitude and longitude of the point of intersection directly under the ...
5
votes
2answers
4k views

How to calculate polygon areas and perimeters?

If I load a polygon layer and make a new column, how do I fill that column with the 1) area of each polygon and another column with 2) the length of the perimeter of each polygon?
4
votes
2answers
2k views

How to Partition Line into Segments using ArcGIS for Desktop?

I have a shapefile of U.S. states. I extracted the boundary between two states, resulting in a line segment. For example, the boundary between Georgia and North Carolina. Is there a way to further ...
3
votes
2answers
949 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 ...
2
votes
1answer
902 views

How to avoid duplicate labels on each tile?

When I display my map using tiles a label gets drawn on each tile - is there any way to avoid this? I have attached an example image to show the problem:
1
vote
2answers
766 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 ...
7
votes
3answers
9k 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 ...
6
votes
3answers
2k views

Is it possible to postprocess Trimble .ssf files without Trimble Pathfinder Office?

Is it possible to postprocess Trimble .ssf files without Trimble Pathfinder Office (differential correction - our sporadic use does not defend realtime correction subscription) ? We only need the ...
5
votes
3answers
2k views

Select features by attribute if in Python list

I believe this will amount to largely a sql syntax question. Essentially, I am trying to complete a select by attribute in Python but based on the query of whether an attribute is present in a list. ...
3
votes
1answer
95 views

QGIS display does not reflect projection

I have slight experience with ArcGIS, but am new to QGIS. I'm trying to set the projection of my map, and I understand that this is done by altering the CRS (coordinate reference system) of each ...
3
votes
2answers
2k views

How to display both scalebar in kilometers and grid in lat/long degrees in Quantum GIS 1.8 Composer?

Also, how to display both scalebar in kilometers and both lat/long degrees and northings/eastings in QGIS 1.8 Composer? Layer is projected to UTM. Thank you.
3
votes
1answer
4k views

How to sort a feature class and then calculate a sequential ID field?

I am in ArcMap and I want to sort the records based on a field and then do a Calculate Field with an auto-incrementing value with the sort in-place. Any ideas? It looks like I could get an update ...
3
votes
1answer
9k views

How to add GeoServer wfs layer on OpenLayers?

I can't seem to add a WFS layer like this. It works when i copy all this code locally but as soon as i change the values to point to my own layer within my own GeoServer this is the response viewed ...
2
votes
0answers
122 views

Why do tiles seems to jump around when using ArcGIS cache layer in Openlayers?

I am use Openlayers to add ArcGIS tilecache layers using arcgiscache class or another way which is jsonp. I can show the map properly, but when I pan, zoom or drag the map, the tiles seem to jump ...
2
votes
1answer
3k views

XMLHttpRequest cannot load http://localhost: /geoserver/wfs. Origin http://localhost is not allowed by Access-Control-Allow-Origin [duplicate]

Possible Duplicate: Setup own Openlayers Proxyhost Error WFS Request, PROXY problems I have this error: XMLHttpRequest cannot load http:// localhost: /geoserver/wfs Origin http:// ...
1
vote
1answer
575 views

How to evaluate raster calculator expressions from the console?

How can I execute from the console an expression that should be used with the raster calculator? I'm searching for something like this: qgis.someRasterCalcClass.evaluate("boh@1 + boh@2", ...
41
votes
13answers
7k views

What are the best resources for learning GIS programming with Python?

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)
40
votes
3answers
8k views

Openlayers Animation Examples and Algorithms

i wonder for a long time if people in this community uses openlayers for animation needs. we have know this that animating on browser is a little bit exhausting for it but when a map meets with ...
41
votes
10answers
3k 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
11answers
3k 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 ...
28
votes
9answers
8k views

Open source methods for kriging?

I have a point dataset which I'd like to Krige, ideally using an open-source software package. If possible, I'd also like to choose the semi-variogram model during the process to improve the ...
18
votes
7answers
3k views

What are my options for 3D web Maps?

I wish to have a Online 3D Map, which would show my Data, i.e both Raster and Vector, draped on a DEM that I have. Due to the requirements of using my own DEM & Raster data, Google Earth API is ...
18
votes
9answers
4k 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 ...
13
votes
4answers
7k views

How to get the nearest point on a linestring to a given point?

I've been using PostGIS in a long time now but never had to use the LINESTRING geometry ... yet! :) Here's what I would like to do : I have a table of linestrings (representing streets of a given ...
26
votes
1answer
6k 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 ...
23
votes
7answers
3k views

How to compare two spatial point patterns?

If I have two point pattern distributions within the same geographic region, how would I go about visually and quantitatively comparing those two distributions? Also assume I have many points within ...
10
votes
1answer
5k views

How do I calculate the latitude and longitude of points using QGIS?

I'm trying to figure out how to calculate the lat/long of points using the QGIS field calculator. Is there an easy way to do this? I saw a previous related question, but it deals with a more advanced ...
20
votes
5answers
7k views

How to migrate GDB data into PostGIS without ESRI apps?

Can you tell me how I can load geodatabase data into PostGIS without having to install ESRI apps? The solution I found online talked about using ArcGIS to convert GDB to SHP and then importing SHP to ...
18
votes
6answers
6k views

How to convert image of map into vector format?

What is the best way of converting a gif of a map into a vector format, such as a shapefile? The only relevant parts that I am interested in are the outline of the island so I realize some manual ...
14
votes
5answers
2k views

Standard SLDs for OpenStreetMaps?

We have downloaded OSM data for our region and loaded them into PostGIS using osm2pgsql. So far so good. On top we have GeoServer and we would like to expose the OSM data using WMS. We would as well ...
14
votes
1answer
1k views

Calling arcpy/python from .NET?

Are there any available examples that show how python can be integrated into a .NET ArcGIS Addin or Extension? I have a series of python scripts that I would like to call from form events (e.g. button ...
14
votes
3answers
8k views

Mapnik, Mapserver or Geoserver

I'm currently developping an ArcGIS based flex webviewer. ArcGIS is great for most of the things but there are some issues like performance and license costs. That's why I'm looking into possible ...
24
votes
8answers
9k views

Open Source Tool capable of reading Esri File Geodatabase (.gdb)?

I have an ESRI File Geodatabase (.gdb) file that I would like to convert to shapefile (or any other non-proprietary format). Are there any Open Source tools to do so?
22
votes
1answer
3k views

Convert GeoJSON to TopoJSON

Question How do you convert GeoJSON data to TopoJSON? Why Topojson files are often smaller than geojson and the conversion allows you to incrementally simplify a dataset, if you wish.
18
votes
3answers
3k views

How can I calculate the average width of a polygon?

I'm interested in examining the average width of a polygon that represents the road surface. I also have the road centerline as a vector (which is sometimes not exactly in the center). In this example ...
7
votes
5answers
6k views

Comparison of Open Source Desktop GIS Packages

I'm curious as to what comparisons are out there between different Open Source Desktop GIS software packages. I'm aware that there has been a QGIS and gvSIG comparison on this site but I am looking ...
22
votes
3answers
5k views

Visualising WKT geometry string in QGIS

A very simple question: Is there a simple tool in QGIS to graphically visualise geometry formatted as text? Example geometry: "POLYGON((571178 6337246,571178 6402217,598061 6402217,598061 ...
17
votes
5answers
2k views

Is there a source for historical shapefiles and tiles?

Is there a source for historical shapefiles and tiles? Like the ancient Greece/Rome, medieval Europe and Japan? Ideally with multiple snapshots during different periods in their development, since ...
15
votes
3answers
2k views

Visual Impact Assessment in QGIS or GRASS

Is it possible using QGIS or GRASS to perform a Zone of Visual Impact assessment? E.g. where can a 100m high structure be seen at a viewing height of 1.8m within 30km, taking into account elevation ...
11
votes
4answers
2k views

Simplifying polygons to linestring

I would like to simplify some polygons that represent rivers into linestrings. I assume that holes in polygons can be omitted. Anybody has some good idea how to simply do it? It would be nice, if it ...
8
votes
4answers
2k views

How to create arcs between two points in Python?

I've been working on an python script automating the visualization of live point data. I have a table with two coordinate pairs. I'd like to connect these two point with an arc of a circle or similar ...
17
votes
7answers
3k views

File Geodatabase Open API

Any ESRI boffins (insiders) know when this will be available? 2010, 2011? FINAL UPDATE now released 20th January 2011 - Can be downloaded here - ...
11
votes
4answers
12k views

How do you decide what interpolation method to use for resampling raster data?

The question pretty much says it all; are there hard and fast rules about which interpolation methods are suited to each kind of raster data? Any Golden rules, rules of thumb? Good books or articles ...
10
votes
8answers
7k views

Is there a comprehensive list of latitude and longitude values for cities around the world?

I'm developing an application that calculates the distance between cities using their respective Longitude and Latitude values. But the problem is where to get a comprehensive list of latitude and ...
6
votes
1answer
3k views

Openlayers wfs vector layer

I'm trying to add a vector layer with a wfs layer and it's not working.Can anyone point a solution? Openlayers code: var wfs = new OpenLayers.Layer.Vector( "Stavros Features", ...
5
votes
1answer
737 views

Creating a table containing all filenames (and possibly metadata) in a 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 ...
44
votes
8answers
2k views

One dimensional map of the world?

Bit of a strange question but hope this is OK to ask here. Has anyone heard of a '1-dimensional' projection of the world map - that is mapping all the points on the globe to a single line? I was ...

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