7,399 reputation
660150
bio website djq.me
location Cambridge, MA
age
visits member for 4 years, 9 months
seen Jun 29 at 23:25

interested in postgis, geodjango, qgis, python and R

cofounder of coUrbanize

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Jan
30
comment Visualization to inference workflow
Can you explain a little more why the paper you describe is untrustworthy? It's not obvious to me why this is the case. If the relationship exists statistically, does it matter what 'mental model' you used to achieve identifying it? I understand that it does not explain the mechanism, but that is a separate issue.
Jan
30
comment Getting line FID from polygon ITopologyGraph
Can you say what software or programming language you want to do this in? It sounds like an adjacency matrix might help, but I don't fully understand the problem.
Jan
29
comment How to select a raster file that is under a polygon in a vector file?
possible duplicate of How to combine a vector and a raster file?
Jan
24
comment Append to text file using ArcGIS and Python
When you say, "it automatically erases the file" do you mean the .csv file that you are appending to?
Jan
20
comment How to divide a polygon into specific sizes using ArcGIS?
Perfect. Thanks for the clear explanation and the suggestions of what to search for.
Jan
19
comment Using the Proj4js library to convert from Google Maps to projected values
I just added some.
Jan
18
comment Using the Proj4js library to convert from Google Maps to projected values
Good point - I was not aware of that. However, I'm still not getting values that are correct even considering that.
Jan
18
comment Using the Proj4js library to convert from Google Maps to projected values
To clarify though, I export this using ArcGIS' 'Export to KML function', which I now assume turns it into epsg:900913
Jan
18
comment Using the Proj4js library to convert from Google Maps to projected values
I'm certain that the input projection data is in the British National Grid which I believe is EPSG:27700. However, when it is laid ontop of google maps I assumed I should use their lat/long values, projected, to convert it back into the original British National grid format. Is this correct?
Jan
18
comment Using the Proj4js library to convert from Google Maps to projected values
I don't quite follow what you mean about what the values should be between (-5 and 5), for example. Looking at the bounding box in ArcGIS I have the following information: Projected Coordinate System: British National Grid (ORD SURV GB) Projection: Transverse_Mercator false_easting: 400000.00000000 false_northing: -100000.00000000 central_meridian: -2.00000000 scale_factor: 0.99960127 latitude_of_origin: 49.00000000 Linear Unit: Meter The box is around London, and has the coordinates (500000, 150000) for southwest corner, and (560000, 210000) in the northeast corner.
Jan
18
comment Using the Proj4js library to convert from Google Maps to projected values
Sorry, I didn't mean to sound so casual; I looked on Spatial Reference for EPSG:900913, and it is defined there as 'SR-ORG:6627'. I used that for my source (defined in the webpage) amd similarly 'epsg:2770' for destination. I compared the values and they are different. For example, my webpage returns Xmin: 622726.0903127209, Ymin: 622726.0903127209 while my values should be Xmin: 500000, Ymin: 150000
Jan
18
comment Using the Proj4js library to convert from Google Maps to projected values
I tried using spatialreference.org/ref/sr-org/6627 and it still is not returning correct values.
Jan
18
comment Using the Proj4js library to convert from Google Maps to projected values
Thanks @Vadim, i have edited my question to include that. You are correct that I wrote the wrong one in my text.
Jan
18
comment Using the Proj4js library to convert from Google Maps to projected values
I'm not sure at all, so I will try that. Googling (!) for it has given me a lot of different suggestions.
Jan
17
comment Java, GIS knowledge…What next?
Could you elaborate on whether you are interested in web-based GIS applications or non-web based?
Jan
16
comment Converting google map api coordinates into meters
Thanks - that worked perfectly. It's a really useful library!
Jan
12
comment Where can I find historic maps of city size?
This data is useful, but there are not an areas associated with the counts (as far as I can see)
Jan
12
comment Where can I find historic maps of city size?
I'm not able to find the archive; there is a pay-site for old maps. Is there another part of the site?
Jan
10
comment Where can I find historic maps of city size?
I'm interested in the earliest recorded records of a city existing (e.g. 1500s onwards), to the present day.
Jan
5
comment Determining statistical relationships between rasters using R vs ArcGIS Desktop?
It's true - speed is not really an issue. It takes about 10s to load two rasters and a 10-15 seconds per operation thus far. If I keep things in perspective, I've waited just as long in ArcGIS for things to happen! I plan to use sampling more, though which will remove any slight delay.