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From: Fraser Dickson on 30 Mar 2010 05:52
Hi I found some code in the file ezxchange for viewing a google map ( static) in matlab bu computing a url and using urlwrite to save the image however i have a problem in that i keep getting the error
"error downloading url"

however if i take the url that the code makes and put that directly in a browser it the map is displayed fine

this was the code i got off the net

function [XX YY M Mcolor] = get_google_map(lat, lon, varargin)
%% Gets a google map using the Google Static Maps API
%
% REQUIREMENTS:
% 1) deg2utm() (Conversion from degrees to UTM coordinates, found on
% MATLAB Central.
%
% 2) THIS FUNCTION REQUIRES A GOOGLE MAPS API KEY! (READ ON)
% To query and return a Google Map using the Google Static Map API, Google
% requires that you have a valid MAPS API KEY. The key is free and only
% requires a Google account and a valid domain (e.g. http://ccom.unh.edu )
% from which your queries will come. Note, this last requirement places
% serious limitations on the portability of this function, as it is
% necessarily tied to a domain and therefore (usually) a physical location.
%
% A Google Maps API Key may be obtained here:
% http://code.google.com/apis/maps/signup.html
%
% Once you obtain your key, replace the text assigned to the MAPS_API_KEY
% variable below with your own.
%
% USAGE:
%
% [XX YY M Mcolor] = get_google_map( latitude, longitude, ...
% Property, Value,...
% Property, Value)
%
% PROPERTIES:
% Height (640) Height of the image in pixels (max 640)
% Width (640) Width of the image in pixels (max 640)
% Zoom (15) Zoom Level (1-19) Zoom of 15 = ~3.4m/pixel.
% MapType ('satellite') Type of map to return. Any of [roadmap, mobile,
% satellite, terrain, hybrid, mapmaker-roadmap,
% mapmaker-hybrid) See the Google Maps API for
% more information.
% Marker The marker argument is a text string with fields
% conforming to the Google Maps API. The following are
% valid examples:
% '43.0738740,-70.713993' (dflt midsize orange marker)
% '43.0738740,-70.713993,blue' (midsize blue marker)
% '43.0738740,-70.713993,yellowa' (midsize yellow
% marker with label "A")
% '43.0738740,-70.713993,tinyredb' (tiny red marker
% with label "B")
%
% RESULTS:
% XX Estimate of Easting pixel coordinates in UTM
% YY Estimate of Northing pixel coordinates in UTM
% M Image data matrix (height x width)
% Mcolor Image colormap
%
% EXAMPLE:
%
% % Get the map
% [XX YY M Mcolor] = get_google_map(43.0738740,-70.713993);
% % Plot the result
% surf(XX,YY,M,'edgecolor','none'); view(0,90);
% colormap(Mcolor)
%
%
%
% References:
% http://code.google.com/apis/maps/documentation/staticmaps
%
% KNOWN BUGS AND ISSUES:
% 1) MAP Bounds. The bounds reported by this function are an approximation
% based on repeated trials, as there is no way (to my knowledge) in which
% to query Google for the bounds of the map image exactly. This method is
% potentially ripe with errors. For example, it may not produce correct
% bounds at latitudes far from 40 degrees N/S where it was calibrated.
% 2) No provision has been programmed to handle locations near the date
% line, nor boundaries between UTM zones. Images that cross these will
% likely produce improper bounds.
%
% * Val Schmidt
% * University of New Hampshire
% * Center for Coastal and Ocean Mapping
% * 2009

% Google Maps Key for http://ccom.unh.edu
MAPS_API_KEY = ['ABQIAAAAgjJdMDG4XFg3DYYdLGwa8RTR4qNa0YPO2GvXB6kZVmHq2RMeSBSITPO142vFjK9HnDCoEOMZK1TA9w'];

% HANDLE ARGUMENTS

height = 640;
width = 640;
zoomlevel = 15;
maptype = 'satellite';

markeridx = 1;
markerlist = {};
if nargin > 2
for idx = 1:2:length(varargin)
switch lower(varargin{idx})
case 'height'
height = varargin{idx+1};
case 'width'
width = varargin{idx+1};
case 'zoom'
zoomlevel = varargin{idx+1};
case 'maptype'
maptype = varargin{idx+1};
case 'marker'
markerlist{markeridx} = varargin{idx+1};
markeridx = markeridx + 1;
otherwise
error(['Unrecognized variable: ' varargin{idx}])
end
end
end


if zoomlevel <1 || zoomlevel > 19
error('Zoom Level must be > 0 and < 20.')
end

if mod(zoomlevel,1) ~= 0
zoomlevel = round(zoomlevel)
warning(['Zoom Level must be an integer. Rounding to '...
num2str(zoomlevel)]);
end

% ESTIMATE BOUNDS OF IMAGE:
%
% Normally one must specify a center (lat,lon) and zoom level for a map.
% Zoom Notes:
% ZL: 15, hxw = 640x640, image dim: 2224.91 x 2224.21 (mean 2224.56)
% ZL: 16, hxw = 640x640, image dim: 1128.01m x 1111.25m (mean 1119.63)
% This gives an equation of roughly (ZL-15)*3.4759 m/pix * pixels
% So for an image at ZL 16, the LHS bound is
% LHS = centerlonineastings - (zl-15) * 3.4759 * 640/2;
[lonutm latutm zone] = deg2utm(lat,lon);
Hdim = (2^15/2^zoomlevel) * 3.4759 * width;
Vdim = (2^15/2^zoomlevel) * 3.4759 * height;

ell = lonutm - Hdim/2;
nll = latutm - Vdim/2;
eur = lonutm + Hdim/2;
nur = latutm + Vdim/2;

YY = linspace(nll,nur,height);
XX = linspace(ell,eur,width);

% CONSTRUCT QUERY URL
preamble = 'http://maps.google.com/staticmap';
location = ['?center=' num2str(lat,10) ',' num2str(lon,10)];
zoom = ['&zoom=' num2str(zoomlevel)];
size = ['&size=' num2str(width) 'x' num2str(height)];
maptype = ['&maptype=' maptype ];
markers = '&markers=';
for idx = 1:length(markerlist)
if idx < length(markerlist)
markers = [markers markerlist{idx} '%7C'];
else
markers = [markers markerlist{idx}];
end
end
format = '&format=gif';
key = ['&key=' MAPS_API_KEY];
sensor = '&sensor=false';
url = [preamble location zoom size maptype format markers key sensor];
disp(url)
% GET THE IMAGE
filename = urlwrite(url,'tmp.gif');
[M Mcolor] = imread(filename);
M = cast(M,'double');

% CLEAN UP
delete(filename);
From: us on 30 Mar 2010 06:14
"Fraser Dickson" <fraser.dickson(a)gmail.com> wrote in message <hoshk3$et3$1(a)fred.mathworks.com>...
> Hi I found some code in the file ezxchange for viewing a google map ( static) in matlab bu computing a url and using urlwrite to save the image however i have a problem in that i keep getting the error
> "error downloading url"
>
> however if i take the url that the code makes and put that directly in a browser it the map is displayed fine
>
> this was the code i got off the net

ask the author of the FEX code...

us
From: Oliver Woodford on 30 Mar 2010 06:24
"Fraser Dickson" wrote:
> Hi I found some code in the file ezxchange for viewing a google map ( static) in matlab bu computing a url and using urlwrite to save the image however i have a problem in that i keep getting the error
> "error downloading url"
>
> however if i take the url that the code makes and put that directly in a browser it the map is displayed fine
>
> this was the code i got off the net
>
> function [XX YY M Mcolor] = get_google_map(lat, lon, varargin)
> %% Gets a google map using the Google Static Maps API
> %
> % REQUIREMENTS:
> % 1) deg2utm() (Conversion from degrees to UTM coordinates, found on
> % MATLAB Central.
> %
> % 2) THIS FUNCTION REQUIRES A GOOGLE MAPS API KEY! (READ ON)
> % To query and return a Google Map using the Google Static Map API, Google
> % requires that you have a valid MAPS API KEY. The key is free and only
> % requires a Google account and a valid domain (e.g. http://ccom.unh.edu )
> % from which your queries will come. Note, this last requirement places
> % serious limitations on the portability of this function, as it is
> % necessarily tied to a domain and therefore (usually) a physical location.
> %
> % A Google Maps API Key may be obtained here:
> % http://code.google.com/apis/maps/signup.html
> %
> % Once you obtain your key, replace the text assigned to the MAPS_API_KEY
> % variable below with your own.
> %
> % USAGE:
> %
> % [XX YY M Mcolor] = get_google_map( latitude, longitude, ...
> % Property, Value,...
> % Property, Value)
> %
> % PROPERTIES:
> % Height (640) Height of the image in pixels (max 640)
> % Width (640) Width of the image in pixels (max 640)
> % Zoom (15) Zoom Level (1-19) Zoom of 15 = ~3.4m/pixel.
> % MapType ('satellite') Type of map to return. Any of [roadmap, mobile,
> % satellite, terrain, hybrid, mapmaker-roadmap,
> % mapmaker-hybrid) See the Google Maps API for
> % more information.
> % Marker The marker argument is a text string with fields
> % conforming to the Google Maps API. The following are
> % valid examples:
> % '43.0738740,-70.713993' (dflt midsize orange marker)
> % '43.0738740,-70.713993,blue' (midsize blue marker)
> % '43.0738740,-70.713993,yellowa' (midsize yellow
> % marker with label "A")
> % '43.0738740,-70.713993,tinyredb' (tiny red marker
> % with label "B")
> %
> % RESULTS:
> % XX Estimate of Easting pixel coordinates in UTM
> % YY Estimate of Northing pixel coordinates in UTM
> % M Image data matrix (height x width)
> % Mcolor Image colormap
> %
> % EXAMPLE:
> %
> % % Get the map
> % [XX YY M Mcolor] = get_google_map(43.0738740,-70.713993);
> % % Plot the result
> % surf(XX,YY,M,'edgecolor','none'); view(0,90);
> % colormap(Mcolor)
> %
> %
> %
> % References:
> % http://code.google.com/apis/maps/documentation/staticmaps
> %
> % KNOWN BUGS AND ISSUES:
> % 1) MAP Bounds. The bounds reported by this function are an approximation
> % based on repeated trials, as there is no way (to my knowledge) in which
> % to query Google for the bounds of the map image exactly. This method is
> % potentially ripe with errors. For example, it may not produce correct
> % bounds at latitudes far from 40 degrees N/S where it was calibrated.
> % 2) No provision has been programmed to handle locations near the date
> % line, nor boundaries between UTM zones. Images that cross these will
> % likely produce improper bounds.
> %
> % * Val Schmidt
> % * University of New Hampshire
> % * Center for Coastal and Ocean Mapping
> % * 2009
>
> % Google Maps Key for http://ccom.unh.edu
> MAPS_API_KEY = ['ABQIAAAAgjJdMDG4XFg3DYYdLGwa8RTR4qNa0YPO2GvXB6kZVmHq2RMeSBSITPO142vFjK9HnDCoEOMZK1TA9w'];
>
> % HANDLE ARGUMENTS
>
> height = 640;
> width = 640;
> zoomlevel = 15;
> maptype = 'satellite';
>
> markeridx = 1;
> markerlist = {};
> if nargin > 2
> for idx = 1:2:length(varargin)
> switch lower(varargin{idx})
> case 'height'
> height = varargin{idx+1};
> case 'width'
> width = varargin{idx+1};
> case 'zoom'
> zoomlevel = varargin{idx+1};
> case 'maptype'
> maptype = varargin{idx+1};
> case 'marker'
> markerlist{markeridx} = varargin{idx+1};
> markeridx = markeridx + 1;
> otherwise
> error(['Unrecognized variable: ' varargin{idx}])
> end
> end
> end
>
>
> if zoomlevel <1 || zoomlevel > 19
> error('Zoom Level must be > 0 and < 20.')
> end
>
> if mod(zoomlevel,1) ~= 0
> zoomlevel = round(zoomlevel)
> warning(['Zoom Level must be an integer. Rounding to '...
> num2str(zoomlevel)]);
> end
>
> % ESTIMATE BOUNDS OF IMAGE:
> %
> % Normally one must specify a center (lat,lon) and zoom level for a map.
> % Zoom Notes:
> % ZL: 15, hxw = 640x640, image dim: 2224.91 x 2224.21 (mean 2224.56)
> % ZL: 16, hxw = 640x640, image dim: 1128.01m x 1111.25m (mean 1119.63)
> % This gives an equation of roughly (ZL-15)*3.4759 m/pix * pixels
> % So for an image at ZL 16, the LHS bound is
> % LHS = centerlonineastings - (zl-15) * 3.4759 * 640/2;
> [lonutm latutm zone] = deg2utm(lat,lon);
> Hdim = (2^15/2^zoomlevel) * 3.4759 * width;
> Vdim = (2^15/2^zoomlevel) * 3.4759 * height;
>
> ell = lonutm - Hdim/2;
> nll = latutm - Vdim/2;
> eur = lonutm + Hdim/2;
> nur = latutm + Vdim/2;
>
> YY = linspace(nll,nur,height);
> XX = linspace(ell,eur,width);
>
> % CONSTRUCT QUERY URL
> preamble = 'http://maps.google.com/staticmap';
> location = ['?center=' num2str(lat,10) ',' num2str(lon,10)];
> zoom = ['&zoom=' num2str(zoomlevel)];
> size = ['&size=' num2str(width) 'x' num2str(height)];
> maptype = ['&maptype=' maptype ];
> markers = '&markers=';
> for idx = 1:length(markerlist)
> if idx < length(markerlist)
> markers = [markers markerlist{idx} '%7C'];
> else
> markers = [markers markerlist{idx}];
> end
> end
> format = '&format=gif';
> key = ['&key=' MAPS_API_KEY];
> sensor = '&sensor=false';
> url = [preamble location zoom size maptype format markers key sensor];
> disp(url)
> % GET THE IMAGE
> filename = urlwrite(url,'tmp.gif');
> [M Mcolor] = imread(filename);
> M = cast(M,'double');
>
> % CLEAN UP
> delete(filename);

A silly question I'm sure, but have you fulfilled requirement 2 of the help text?
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