Top new questions this week:

QGIS area calculation differs when on the fly CRS transformation enabled

When I open QGIS, add the layer, and calculate the areas of the shapefile via field calculator I get a different area than when I open QGIS and check "Enable on the fly CRS transformation" and ...

qgis coordinate-system area

asked by lara.faelivrin 5 votes answered by dof1985 1 vote

Dump a GeoJSON FeatureCollection from Spatialite query with Python

Given a Spatialite database, holding a table with a geometry column and some other attribute columns. I want to query that table in a Python script and get a GeoJSON FeatureCollection string in return ...

python geojson spatialite

asked by Dirk 4 votes answered by Dirk 2 votes

What does it mean that shapefiles are "mostly" open specification?

Esri Shapefiles are commonly considered the standard format for GIS vector data. I noticed on Wikipedia and the OpenStreetMap wiki it is noted (emphasis mine): The shapefile format is a popular ...

shapefile specification

asked by Ivan 4 votes answered by dof1985 4 votes

Buffering Points Directionally

I have about 10,000 points that I want to apply a partial circular buffer to based on an angle, from -30 to 135°. A similar question for polygons seems to have been answered here, but I cannot make ...

arcgis-desktop arcpy buffer

asked by KJYDavis 4 votes answered by GISGe 2 votes

ArcGIS Model isn't accepting my SQL Query

I'm running a model that breaks a dataset into several dbf tables based on a query. However, only half of the query is being honored. The PopDenZone field is not being accepted and I am getting other ...

arcgis-desktop arcgis-10.1 modelbuilder sql

asked by Craig 4 votes answered by juturna 5 votes

Calculate geometry on some features have same X and Y for start and end?

I did "Calculate Geometry" on a line shapefile to obtain the coordinates X and Y for the start and the end of all the lines of the shape. But some lines resulted with the same X on the start and on ...

arcgis-desktop arcmap shapefile coordinates

asked by Andreia Medeiros 3 votes answered by Dan C 2 votes

Local Ortho projection to Proj4

We are trying to use proj4 to project a local coordinate system to EPSG4326. We believe we have most of the string created correctly in QGIS and as follows; +proj=ortho +datum=WGS84 ...

esri proj4 epsg

asked by Frank 3 votes answered by AndreJ 2 votes

Greatest hits from previous weeks:

What is the maximum Theoretical accuracy of GPS?

I was talking with a potential client, and they requested that we plot some points with GPS, with a maximum (or should that be minimum?) accuracy of 2 m. This is an area with no WAAS, and I was under ...

gps accuracy

asked by Devdatta Tengshe 16 votes answered by Baltok 12 votes

How to Start Web Mapping?

I want to start working on a web map at work to map some of our statistics by city. I have an idea, but I'm not exactly sure where to start. Are there any definitive resources that provide step ...

web-mapping learning-resources

asked by Brian L 68 votes answered by underdark 44 votes

Can you answer these?

Does CartoDB support the SQL MERGE command?

I am developing a mechanism that uploads records to cartodb - first by importing the records to a new table, and then insert the records from the new table to an existing table. The problem is that ...

cartodb sql merge

asked by Oren 1 vote

ArcSDE reconcile versions and keep edit version in its current state

Reconciling versions makes both target and source(s) point to the same state. I have an arcpy script that essentially will create a version from a parent of the db - in a state that is empty - adds ...

arcpy arcsde versioning pyodbc

asked by branchini 2 votes

How to create raster from table containing cell values in PostGIS?

I am having a table with integer values. These values are in between 0 and 2. I want to create a raster out of that table with integers as cell values. Or else how to create polygons out of that table ...

postgis raster postgresql

asked by Bikram Gangwar 2 votes