3,897 reputation
719
bio website barry.rowlingson.com
location Lancaster, United Kingdom
age 48
visits member for 4 years, 3 months
seen 12 hours ago

Here I am.


16h
comment Calculate a polygon around a point - and conver to WKT
agh! they changed the args for gBuffer, you now have to spell it out unless you also want byid=TRUE
16h
revised Calculate a polygon around a point - and conver to WKT
args of gBuffer changed.
20h
comment Calculate a polygon around a point - and conver to WKT
Create a reproducible example and post it as a new question.
2d
comment Problems exporting aerial imagery from QGIS
Hmm well it wasn't obvious how you were using the print composer. So you go: start QGIS; Menu: Web: Open Layers: Google Satellite; zoom, add your rivers layer, switch to print composer, add map, see it all nicely laid out. Then "Export as PDF", and PDF appears as above? I can't duplicate that. Can you screengrab your QGIS main and QGIS composer window and add those to the question?
2d
comment Problems exporting aerial imagery from QGIS
Can you go through your workflow in a bit more detail? Which menu options you are using for example. Are you trying to get Google aerial imagery? You may want to also read the Google Terms of Service.
2d
answered How to insert a statement (e.g. copyright) which remains visible in mapping window?
2d
comment How to make a panoramic view?
Starting from what data? For an engraving, colour is no use, right?
Dec
15
comment Raster to polygon using R
If its simply a memory exhaustion problem then a) get more memory b) downsample your raster c) chop your raster into overlapping tiles, polygonise and merge.
Dec
11
answered Cannot add plugins to QGIS on Ubuntu 11.10 Oneric
Nov
28
answered Formulae to convert WGS84 coordinates (B,L) to spherical coordinates (phi,lambda)?
Nov
25
comment Extract values from raster into points: data loss using extract function from raster package
Edit your question to set up an example like I've done that illustrates the problem. Is it just a case that your new sample cell areas are different, and you've forgotten that the original raster is km/**per unit area** and you need to scale up by the change in cell area? I don't know, because you haven't given us any code.
Nov
20
comment Extracting raster values with polylines in QGIS
How is "average slope" defined? It might just be the height difference from start to finish divided total distance, in which case you only need to sample the height at two points. Otherwise there's some calculus involved which you can probably estimate with finite steps...
Nov
20
answered Extract values from raster into points: data loss using extract function from raster package
Nov
20
comment Extract values from raster into points: data loss using extract function from raster package
@CincoSauces yes. But how can the sum of the values of a small number of points sampled over a grid ever be anything but less than the sum of the grid cells? We really need to see some code and some clarification. I don't understand why this Q has been upvoted.
Nov
20
comment Extract values from raster into points: data loss using extract function from raster package
If you are only sampling 49,000 points then obviously they are going to sum to less than 66,000 cells. What did you expect, and can you give us a reproducible example maybe using random data on a much smaller grid?
Nov
13
comment Saving text labels out of qgis
If the text is an attribute of the point features then its in the DBF part of the shapefile. Try opening the .DBF in a spreadsheet program (I don't know if MS Office can read it, but Libre Office can).
Nov
10
comment R custom color theme in levelplot
What are you going to do with this colour ramp once you've go it? Different plot functions have different ways of mapping values to colours. ggplot2 uses its own scales concept, base graphics uses a fixed palette (usually) and so on...
Nov
9
comment 1km circles around lat-long-points in many places in world
I have a problem with "exactly 1000m" and the phrase "circle-polygons". Your circle-polygons need infinite segments to be exactly 1000m, and converting to UTM (or any other planar system) is going to introduce even more errors. Be careful with the use of "exact".
Nov
9
answered How can i use Kriging inside a Postgis database?
Nov
9
comment How can i use Kriging inside a Postgis database?
Do you want to interpolate from just four measurement locations? That only gives you six points (4*3/2) for working out the covariance for the Kriging equations. It'll be rubbish.