I have a path (which is essentially a line). I am able to draw an arrowhead with the help of marker-end attribute of path. But now I want to make a + sign in the middle of the path. I think for that purpose, marker-mid should be used.
Here is the code and output when I use marker-end.
Here is the code and output when I use marker-mid.
marker-mid specifies the marker type that should be placed for the points in a path that are not the first or last point.
In other words, if you have a path that consists of four points (thus three lines), marker-mid markers will be placed on the middle two points.
There is currently no way to automatically place markers in the middle of a line segment as you wish. You would need to either place an appropriate shape at that point yourself, or split the line into two half-lines.
SVG 2, which is still in development, will likely have this feature, but you can't do it yet.
I have a json file with 80ish adjacent counties, represented as individual polygons. Each county, as expected, shares borders with other counties.
I'd like to convert each of those polygons to paths, creating paths symbolizing the borders of every county. At this point, I'd be left with many overlapping or duplicate paths where counties shared borders.
I'd like to find a systematic way to delete these overlapping paths so each line representing a border is only displayed once. By doing so, I'll be able to style the borders individually to fix a problem described in a previous question.
Does such a thing exist? I'm aware of the possibility of deleting shared borders in Illustrator, but many of the county polygons share borders with 3+ other counties, making this incredibly tedious.
Thanks.
So, I eventually tackled this problem using ArcMap. My steps:
Create a shapefile from the json I was using and load into ArcMap
Import the shapefile into a geodatabase
Put the file into a feature dataset
Create a topology (right click on Feature Dataset > New > Topology)
Add a rule to the topology against overlapping lines
Find all errors (overlapping lines)
Use the error inspector to select each overlapping line and Subtract (right click on error) one of the lines
Took me about 5 minutes to do remove a hundred or so.
I have a set of data points where each point is expressed as a lat/lng. Each of these points has a value associated with it that changes over time. I would like to produce a heatmap animation overlay on top of a map that reflects this change in value over time. Note: I am fine with producing a series of static "snapshots" and piecing them together frame-by-frame into an animation, so the heatmap library itself does not have to support animation.
My first attempt was to use the HeatMapLayer which is a part of the Google Maps visualization library. However as per the question Heatmap based on average weights and not on the number of data points, it would seem that this particular visualization library insists on weighing the density of points in determining what color to use surrounding a given point.
I am after a solution that only considers the value of the points rather than the density. To give an example, assume one wanted to visualize the ambient temperature of a city over time, but there were more thermometers installed in some parts of the city than others. You wouldn't want a small area with many thermometers installed to show up red just because there were many thermometers - you'd want it to show up red only if it was hot there.
Basically, I want a single color for each of my points that reflects the intensity of the point's value, and then a gradient spatial transition between any two point's colors. It doesn't have to be Google Maps - the key criteria is just i) must base colors off point values not point densities ii) must overlay on top of a map and iii) ideally has a programming abstraction that talks in terms of lat/lng's, rather than requiring manual conversion to e.g. Euclidean space.
global tempsYou can do this with multiple:
gmaps.symbol_layer
and then just layer them up:
fig_gmap.add_layer(red_markers)
fig_gmap.add_layer(yellow_markers)
fig_gmap.add_layer(green_markers)
fig_gmap.add_layer(blue_markers)
I haven't been able to successfully pass a value that gives me a good temp color for the heat maps, just always get some variation on the density thing, which is a one trick pony. It would be nice having a way to do this and animate the marker icon without java.
Maybe you should try heatmap.js. It has a plugin for Google Maps: http://www.patrick-wied.at/static/heatmapjs/plugin-gmaps-layer.html
This library uses datasets made of coordinates and values. I think it will behave the way you described.
I'm creating Google Static Maps with a path between markers and have come across certain coordinate combinations that break the path.
The path breaks in this example (markers # Beijing, SF, NY, Azores, Rome):
http://maps.google.com/maps/api/staticmap?path=color:0xff0000cc|weight:3|39.904214,116.407413|37.77493,-122.419416|40.714353,-74.005973|38.721642,-27.220577|41.89052,12.494249&markers=39.904214,116.407413|37.77493,-122.419416|40.714353,-74.005973|38.721642,-27.220577|41.89052,12.494249&maptype=terrain&sensor=false&size=640x404
And works in this example (marker # Rome removed)
http://maps.google.com/maps/api/staticmap?path=color:0xff0000cc|weight:3|39.904214,116.407413|37.77493,-122.419416|40.714353,-74.005973|38.721642,-27.220577&markers=39.904214,116.407413|37.77493,-122.419416|40.714353,-74.005973|38.721642,-27.220577&maptype=terrain&sensor=false&size=640x404
The cause is not crossing over the Greenwich Meridian as I initially thought. It breaks even if I add a marker before that, seemingly any a point East of the automatically calculated centerpoint of the map...but only when the path starts on the other side of -180 longitude.
To prove that, you can see that the Beijing, SF, NY, Azores, Rome path displays correctly when I set the map centerpoint to -170,35
http://maps.google.com/maps/api/staticmap?path=color:0xff0000cc|weight:3|39.904214,116.407413|37.77493,-122.419416|40.714353,-74.005973|38.721642,-27.220577|41.89052,12.494249&markers=39.904214,116.407413|37.77493,-122.419416|40.714353,-74.005973|38.721642,-27.220577|41.89052,12.494249&maptype=terrain&sensor=false&size=640x404¢er=-170,35
Unfortunately, I can't programmatically set center like this because I never know the collection of points I'm going to get, and it would be next to impossible to detect that the passed points would cause a line break.
Any ideas?
First: you can calculate the center even if you don't know the collection of points (locations) at compile time: at runtime you know all the points (otherwise it would be not possible to insert the coordinates into the URL), therefore you can easily iterate over all the points and compute the center. You can computing the average of all coordinates and you get the geometric center (also called centroid): this is the easier way. Another way to do is to check the most distant pair of locations (for both, latitude and longitude) and then set the middle point as center: this requires slightly more coding (for instance to compute the longitude distance you need to take into account the you have to compute the distance in two directions, since it is possible to go 'around the world) and it has an higher complexity.
I don't go deeper in this topic because, even if you compute correctly the center of your points, this does NOT resolve the problem, and moreover the center provided automatically by the Google static map API is always correct: again the center is related to the problem, but it is not the (couse of the) problem.
An aspect that is trivial but important to keep in mind: Google static map draws a path between two locations always by considering the shortest path, i.e. by drawing the shortest straight line.
Therefore if you are in a situation where your path has to go from a location A to a location B, and the shortest path between A and B goes 'around the world' (or better, it goes out from one side of the image), then the path appears 'borken' as in maps that you have shown. In practice A and B are near the left and right margins of the map, and the map can not be centered in some point along the shortest path between A and B because of the others point of the path. And this is what happen when you remove 'Rome': without Rome the map can be centered in a way that the path is not borken.
Formally, I think that the problem appears (i.e. the path is broken), when the projection of the path on the equator is longer than 360 degree of longitudes, and the path always goes in the same direction (i.e. always west to east or always east to west).
Google static map in this situation simply adds another world map next to the first one: if you set the zoom to the minimum, you can see up to three world maps. This is really impractical for several reasons:
you can not zoom out infinitely;
if you want also insert markers into the map they will be drawn only on the 'main' map;
potentially you can have a path that goes around the world (passing in sequence from America, Europe, Asia, and America again and so on...) many times, and it would be really terrible to have so many little maps one after each other;
I googled a lot about this problem, and I didn't find any solution, there is a bug open on the bug tracker, but it is unsolved.
In my opinion the 'right' way to do is simply the following: at most one map and if a path has to goes out from one margin of the map/image, then it should appear on the opposite margin and continues to the destination, drawn on the same map.
So I found a first workaround:
you draw your path, and with the same style (line's color, etc) you also draw the path in a reversed way (Google static map allows to draws multiple paths in the same map), i.e. path=A|B|C&path=C|B|A and this will solve the problem in many situations (i.e. the path exits from one side of the image and enters from the other). Unfortunately this not works always: if you have a path that cross the image margin two consecutive times, then you lose a portion of your path
To solve this problem I found a second workaround:
- not draw simply the path and its reverse, but draw a different path for every pair of locations of the path (and reversed), i.e. for a path A->B->C then: path:A|B,path=B|C,path=C|B,path=B|A and this works always
The drawback is that in this way the URL becomes very long and the limit of 2048 characters for URLs is easily reached.
The best solution would be to compute manually the center, check manually where the path will cross the margin, and only for this portion of the path draw an additional path going between the two locations at the margin (and maybe also the reverse), but I do not think it really worth, although I do not think Google ever will solve this problem.
Hoping someone can point me to an existing resource so I don't have to create it myself.
Basically I need to get a series of lat/long coordinates that represent geo bounding boxes for Japan. The API the data is meant for allows multiple bounding boxes, so I want to create a series of smaller boxes that cover's about 99.9% of the country.
All I need to do is click on a map to indicate the north-east and south-west corners of a box, but I have been unable to find anything that quite does this.
The closest I found was this http://paulisageek.com/hacku/examples/geoBoundingBoxTabs.html. However it doesn't allow multiple bounding boxes, but more importantly doesn't provide the lat/longs that were calculated nor the ability to modify the boxes.
Doesnt look that hard with the new drawing tools library in the google maps api
http://code.google.com/apis/maps/documentation/javascript/overlays.html#drawing_tools
you get the coordinates, in callback event handlers.