58
votes
5answers
7k views
How do I access ArcObjects from Python?
I want to be able to script some things that aren't exposed via arcgisscripting or ArcPy. How do I access ArcObjects from Python?
I'm working with ArcGIS Desktop 9.3.1 right now, but will be ...
7
votes
4answers
4k views
How to fix QGIS error “Entry Point could not be located”?
Today, after returning from vacations, I started my QGIS 1.7 and got this terrible message:
Help, anyone?
36
votes
12answers
3k views
How to Start Web Mapping?
I know I want to start working on a web map at work. We'll be mapping some of our statistics by city.
I have an idea, but I'm not exactly sure where to start. Are there any definitive resources ...
28
votes
2answers
10k views
How to get “.GDB” (Esri File Geodatabase) support in Quantum GIS (osgeo4w - qgis)
Following questions:
Open Source Tool capable of Reading .gdb?
How to access file geodatabase in Qgis?
How to get FGDB support in GDAL 1.9 without compiling?
I have spent around 2 days to find the ...
23
votes
4answers
2k views
Performance of ArcGISScripting and large spatial data sets
I am currently writing a python script using the arcgisscripting module to process a reasonably large data set (~10,000 records in total) normalised over a small number of tables, 8 in total. The ...
87
votes
14answers
23k views
Comparison of JavaScript mapping libraries?
I am working on a web-based mapping system and I'm trying to figure out the best/most appropriate library to use. There are a few of them about and they each have pros and cons. Even after trying a ...
18
votes
8answers
4k views
Best practices for identifying the unknown coordinate system of a Shapefile
I got a Shapefile but it's coordinate system is unknown and there is no .prj file.
How I can identify it now? Are there any tools that could help?
12
votes
3answers
5k views
Layers having the same coordinate system should overlap, but they don't. What's wrong?
I put 4 different layers into my ArcMap document, but only one of them will show up on the map! I should be seeing the other 3 layers as well. When I do a Zoom to layer, I can see one layer, but I ...
124
votes
38answers
19k views
Examples of Beautiful Maps
Often times when we make maps it is based on our subjective interpretation of what is aesthetically pleasing. I would like if people posted examples of beautiful maps, displaying any phenomena in any ...
46
votes
6answers
2k views
Best practices for managing geospatial data
How do you manage your geospatial data? I have terrabytes of data spread out over hundreds of datasets, and have an ad-hoc solution using symbolic links within projects which link back to an ...
34
votes
5answers
3k views
Why is the 'straight line' path across continent so curved?
This is the result of mapping the straight line path from a point in US to Poland using Distance Measurement Tool.
Also, planes from Asia to US would travel almost over North Pole.
Why is the path ...
35
votes
7answers
2k views
What strategies, criteria, or rules to use for selecting coordinate systems?
What strategies, criteria, or rules do you use for selecting coordinate systems for
(a) storing,
(b) analyzing, and
(c) displaying GIS data?
(I humbly offer my reply to a related question ...
27
votes
9answers
10k views
How to install GDAL with Python on windows?
Can anyone please explain to me in step by step instructions how to install GDAL/OGR with Python on Windows. I have Windows Vista and I have tried following the information on the website and it does ...
21
votes
3answers
11k views
Algorithm for offsetting a latitude/longitude by some amount of meters
I'm looking for an algorithm which when given a latitude and longitude pair and a vector translation in meters in Cartesian coordinates (x,y) would give me a new coordinate. Sort of like a reverse ...
11
votes
5answers
9k views
Get list of coordinates for points in a layer?
I've got a layer in QGIS that is comprised of points. Its attribute table doesn't have the corresponding x y coordinates for each point. Is there a way for me to extract a list of coordinates for ...
16
votes
5answers
2k views
Bulk load multiple shapefiles into PostGIS
I've got over a hundred data layers in shapefile format that I want to upload into a PostGIS database. They are all in the same projection, but represent different data layers so they do not have the ...
9
votes
3answers
7k views
How to edit or convert ArcGIS 10 layer style to a SLD's file
Greetings everyone, I am putting together a GIS server using GeoServer and need some help with importing my layer styles from ArcGIS 10 to SLD format. I have one layer in ArcMap properly symbolized ...
89
votes
8answers
16k views
What's the difference between a projection and a datum?
What's the difference between a projection and a datum?
34
votes
10answers
3k views
Where can I find QGIS tutorials and resources?
After several recommendations, I thought I'd familiarize myself with the capabilities of QGIS.
I downloaded the program, but apart from basic loading of data, I got lost (the help file wasn't much ...
50
votes
12answers
12k views
Concave Hull: Definition, Algorithms and Practical Solutions
Convex Hull
A convex hull of a shape is defined as:
In mathematics, the convex hull or convex envelope for a set of points X in a real vector space V is the minimal convex set containing X ...
37
votes
2answers
16k views
How to measure the accuracy of latitude and longitude?
I am very new to GPS stuff. Suppose I have latitude and longitude as 19.0649070739746 and 73.1308670043945 respectively. So now both co-ordinates are 13 decimal places long. But sometimes, I also get ...
18
votes
10answers
2k views
What are the existing solutions to automate generalisation/simplification of geographical data?
I am looking for existing solutions (softwares, libraries, methods, etc.) to automate the generalisation/simplification of geographical data as presented there, and also there.
How do you proceed ...
18
votes
8answers
3k views
Alternatives to pgRouting
I was wondering if there are any alternatives to pgRouting tools.
Thinking about it for a bit, I think the only alternative is to use R or RPY to do the analysis.
Basically I'm trying to solve ...
14
votes
3answers
1k views
Port “Producing Building Shadows” Avenue code to ArcGIS 10
Whuber provided an answer here Producing building shadows? which required using Avenue code. Any idea how to make it work in Arc 10?
Thanks in advance.
22
votes
7answers
2k views
Representation of network flows
This is a sample transportation network flow I've done a year ago based on 26 zones.
For a project I'm working on now, I need to represent the flows over 1,000 zones with directionality.
Any ...
18
votes
10answers
23k views
How do I convert MapInfo TAB and/or MIF to SHP?
How do I convert MapInfo TAB and/or MIF files to SHP using only free tools or ArcGIS itself? I've not had much luck trying to do this in the past and I don't want to have to shell out for the ArcGIS ...
15
votes
3answers
5k views
Why is law of cosines more preferable than haversine when calculating distance between two latitude-longitude points?
In fact, when Sinnott published the
haversine formula, computational
precision was limited. Nowadays,
JavaScript (and most modern computers
& languages) use IEEE 754 64-bit
...
13
votes
12answers
6k views
Shapefiles to Text
How can I convert a shape file (GIS) to text?
or, How can I extract the information in a shape file?
7
votes
4answers
10k views
How to add a simple WFS layer from GeoServer to OpenLayers map?
I'm trying to add one of the included datasets with GeoServer to an OpenLayers map. I've followed the OpenGeo tutorials, seen similar thread on here, but I can't seem to crack it. Can somebody take a ...
3
votes
3answers
4k views
Problems with OpenLayers and WFS - proxy.cgi issues
I am having problems getting WFS data to display on a map using OpenLayers/GeoExt/GeoServer.
I created a proxy script like on this page:
...
94
votes
47answers
6k views
What free programs should every GIS user have installed?
I'm not necessarily referring to ESRI extensions or open-source products, but others that increase your productivity and ability to handle GIS tasks.
For example, Notepad++ for writing code snippets ...
57
votes
34answers
3k views
GIS Pros - what lives on your bookshelf?
What books, journals, electronic resources have you found most valuable for expanding your knowledge in the GI field? To which of them you come back most often?
One item per post please.
35
votes
4answers
11k views
How to build effective heat-maps?
Using ArcGIS, QuantumGIS, Grass, and/or GVSIG
What are some of the tools and processes involved in building effective heat maps?
What are the plugins involved?
What are the major data requirements?
...
16
votes
1answer
3k views
How to divide a polygon into specific sizes using ArcGIS?
I have several thousand irregularly shaped polygons in a shapefile. I want to be able to split each polygon into three areas, and to specify what the size of those areas (they sum to the previous ...
18
votes
1answer
781 views
How to create an accurate Tissot Indicatrix?
A Tissot Indicatrix is useful method for communicating at a glance the kinds of distortion a given projection is prone to (in the figure below, each of the red circles occupies the same area). I've ...
14
votes
7answers
3k views
Looking for system specifications for a modern GIS workstation
My current employer has given me the opportunity to design my own GIS workstation. The problem is I have no idea when it comes to hardware! I have been given a datasheet from Fujitzu which includes ...
7
votes
4answers
4k views
Calculating Lat/Lng X miles from point
I am wanting to find a latitude and longitude point given a bearing, a distance, and a starting latitude and longitude.
This appears to be the opposite of this question (Distance between lat/long ...
4
votes
2answers
758 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 ...
9
votes
3answers
5k 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 ...
14
votes
1answer
493 views
How accurate is approximating the Earth as sphere?
What level of error do I encounter when approximating the earth as a sphere? Specifically, when dealing with the location of points and, for example, the great circle distances between them.
Are ...
3
votes
3answers
2k views
Global DEM to Slope calculation
I have downloaded SRTM GDEM (~90 km resolution). I am using ArcGIS 10. I have tried to use spatial analyst to compute for slope. However, I can not compute for the slope. The output values has only ...
1
vote
2answers
169 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 ...
39
votes
14answers
19k views
List of GIS applications for Android Tablets
I know that ArcGIS will someday be available for Android, but does anyone know of any other GIS apps that are available for Android tablets?
52
votes
11answers
8k views
Examples of badly designed maps
A poorly designed map can not only look visually unappealing, but can convey the wrong message, which could lead to bad decisions being made.
I would like to ask people to post examples (that are in ...
18
votes
2answers
2k views
How to create a regular polygon grid in PostGIS?
How to create, on the shape of a polygon, a regular grid of polygons/squares of an given size, in postgis?
I have thought about a function like Create regular point grid in Postgis only for squares, ...
13
votes
6answers
4k views
Shapefile PRJ to PostGIS SRID lookup table?
I was wondering if there is such a thing as an shapefile PRJ to PostGIS SRID lookup table? Something that can translate the most standard shapefile PRJ definitions into the likely SRID.
When using ...
16
votes
4answers
3k 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, ...
5
votes
3answers
2k views
Python, comtypes and ArcObjects: Error creating AppROT object
I am experimenting with comtypes and ArcObjects under Python 2.6.5 and ArcGIS 10 SP1. I'm using the pure Python method to wrap the ArcObjects OLBs described in this answer, but getting an error in the ...
14
votes
1answer
465 views
What is the most accurate coordinate system for calculating areas of polygons?
I have multiple polygons, all located offshore around the UK. I am trying to calculate the areas of these polygons in square kilometres, without splitting them by UTM zone.
Is it possible to do this ...
13
votes
3answers
8k views
How to clip a raster with vector boundaries?
I am using QGIS. I would like to clip a raster precipitation layer using an admin boundary layer that is vector data. However the geoprocessing tools seem to be usable only for vector data. How can ...
2,673
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