7,111 reputation
353147
bio website djq.me
location Cambridge, MA
age
visits member for 4 years, 3 months
seen 1 hour ago

interested in postgis, geodjango, qgis, python and R

cofounder of coUrbanize

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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 Statistical relationships between rasters
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.
Jan
5
comment Designing Better Maps
I think the question needs rephrasing as the first sentence is a little unclear. Also, a presentation has a somewhat standard structure (presenter and audience). The usage of maps is a lot more broad. Could you narrow it down to some specific instances of map usage?
Jan
3
comment Available US State or National business (or employer) database lists?
just saw the comments discussing Business Analyst now.... nevermind!
Dec
28
comment Using ArcGIS 10 on a virtual machine with OSX
@matt wilkie - which ones were running very slowly? Was it the XP or Win7 ones?
Dec
28
comment ArcMap Geoprocessing vba code/tool - smooth polygon
Added a vb tag.
Dec
20
comment Effectively displaying demographic data on a printed map
@whuber I agree. I did not make the distinction in my question when I wrote it first as I had not thought about it clearly until I read your comment.