Matthew Snape
  • Member for 11 years, 5 months
  • Last seen more than 1 year ago
What strategies, criteria, or rules to use for selecting coordinate systems?
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30 votes

a. It is good practice to store a version of the data in the projection in which it was captured. Re-projection can be a lossy process, and it is important to have the original. I have a preference ...

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How to change the field value of a Shapefile using GDAL/OGR?
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27 votes

The second argument in Open specifies if the data can be updated (written to). Try: dataSource = driver.Open(fn,1)

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Tablet or smart phone GPS vs "real" GPS
18 votes

There are a huge number of devices to choose from, and it is difficult to broadly say that one family of device are more precise than others. It is better to compare accuracy based on real life tests....

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Securing WMS against unauthorized access?
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17 votes

The OGC spec only mandates the use of http. If it is compliant http it should be okay. Some possible methods: HTTP Basic Authentication (password sent as plain text, may have limited client ...

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Batch convert GeoTIFF's to KMZ files
16 votes

Recent versions of gdal_translate have support for KML Superoverlay. Although it is not yet documented on the GDAL website the following can be used: gdal_translate.exe -of KMLSUPEROVERLAY c:\in.tif ...

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Methods for optimizing multcore processing in ArcGIS
11 votes

In my experience the biggest problem is managing stability. If you do six weeks of processing in a single night you will also have six weeks of inexplicable errors and bugs. An alternative ...

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Finding Clusters of N Points Within X Distance using ArcGIS Desktop?
10 votes

Try using the Buffer tool to buffer the points to a tolerance, dissolve to create single polygons for each cluster, and then use a join to count the number of points in the cluster. Then use the ...

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Methods for lat/lon quality control?
9 votes

In a global dataset you will have cases where a point is close to the equator, or Greenwich meridian. At these points a sign change could leave your location in the same country, but at the wrong ...

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How to convert bearing, distance, xy coordinate measurements to point shapefile?
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8 votes

The complex number support in python is a simple way to do operations against Cartesian coordinates. The cmath module provides a function that converts a distance and angle into a vector. This ...

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Quality of free geodata compared to commercial sources
8 votes

It depends how you define quality: Quality as Currency - In many areas OSM is more current than commercial operations. However the level of currency is not necessarily known. Commercial mapping ...

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Converting image of map into vector format
8 votes

Georeference the image and capture by hand. This is by far the best way as it is less prone to error.

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What's the most promising application (use) of OpenStreetMap data?
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7 votes

The most promising application of the data is the map itself. From a developers point of view the other things you mentioned are interesting, but not particularly unique. Maps on their own are ...

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Subset Folder Contents ArcPy
6 votes

Based on explanation by Roy: toprocess = [p for p in [int(filename[0:7]) for filename in txt_list] if p>=3609902 and p<=3610032]

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Installing GDAL and OGR for Python?
6 votes

I had this exact problem when installing GDAL/OGR alongside the ArcGIS python install. My solution for windows was: Download binaries of gdal and python bindings from http://www.gisinternals.com/sdk/...

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Filling in serial letters (AA, AB,AC...,BA,BB,BC...ZZ) to shape using ArcMap
6 votes

Create a numeric field for your island and fill it in. Number each island uniquely depending on the order you want them to appear in the series. Sort based on the island field. Use the following ...

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Need a Benchmark GPS Trajectory data-set?
6 votes

The best I can think of is the GPS traces available from OpenStreetMap. They are not going to be continuous, but there are a large number of them. On the OSM website select "GPS Traces" to have a ...

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UK cities boundries in Ordnance survey
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6 votes

It depends how you define cities. The strategi dataset contains a cities layer. If you wish to have more detail, and include large towns the Meridian 2 dataset contains an urban area layer that ...

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ArcGis--how to lower a DEM's Z value along a line
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5 votes

It would be easier to convert your line directly to raster, and then use spatial analyst tools to modify the DEM Add an attribute to your line shapefiles that defines how mucch elevation should be ...

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Finding GIS data sources for developing nations?
5 votes

Wikimapia is worth checking within developing countries if you have a particular site. It is a community mapping project that focuses on creating a geographically-referenced wiki system. It ...

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Using Data Driven Pages (DDP) to create set of maps with same extent but different layers?
5 votes

A code free method When you turn on data driven pages you can specify a definition query that is dependant on the page number. Simply use that query to hide all features from layers that you do not ...

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Google violates same origin policy using KML with Google Maps?
5 votes

From the Google Maps premier FAQ: The KmlLayer class that generates KML overlays in the Google Maps API uses a Google hosted service to retrieve and parse KML files for rendering. Consequently ...

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Looking for a FREE Cloud based 'Web Mapping Stack' Host
5 votes

Amazon EC2 have a free usage tier that lasts a year for new customers. You could install your own software and would be great for learning the different parts of a typical stack. Google Fusion tables ...

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Detect map scale from raster dataset
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5 votes

A lot of rasters are designed with a particular scale in mind, which you can't detect without metadata describing that fact. However, it is possible to estimate scales that a raster could be printed/...

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postprocessing GPS coordinates with RINEX data to improve precision?
Accepted answer
5 votes

To perform post-processing you typically need a GPS that can record raw pseudorange and carrier cycle data. Very few consumer level GPS support this functionality, and those that do require software ...

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ArcMap label with python if elif
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4 votes

When the text field values are passed to python they are in unicode, and include ths special characters. But you are comparing to values that are encoded as ascii. This works OK for "Eaux de ...

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Looking for a web service for change detection
4 votes

Google Google Earth Engine stores numerous time stamped public domain datasets including: Daily MODIS outputs (very low resolution) such as surface reflectance and NVDI. Periodic Landsat composites, ...

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What types of GIS problems does functional programming address?
4 votes

Not strictly programming, but ArcToolbox follows a more functional design paradigm. Most tools are designed to accept a set of inputs, run a function, and return the outputs without the influence of ...

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Convert X Y Pixels to Easting Northing
Accepted answer
4 votes

GIS file formats contain georeferencing information. This ties image pixel coordinates to grid references in a projection system, in this case British National Grid. There are lots of ways this ...

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Export Map to GeoPDF
4 votes

Starting with version 2 GDAL can create Geospatial PDF's. It is also able to request images directly from WMS servers to retrieve the information from Geoserver.

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How to workaround large mosaic process which is failing?
4 votes

Although its clearly better to use one of the other options mentioned you could try the following: gdalbuildvrt index.vrt *.tif gdal_translate -of "GTiff" -co "COMPRESS=LZW" -co "TILED=YES" -co "...

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