This endpoint implements a standard Web Map Service (WMS) interface, where rasterized image tiles can be requested. Unlike other GPUdb endpoints, there are no JSON request/response messages. For WMS, the request parameters are encoded as HTTP parameters in the request URL. A typical GPUdb WMS request would look like:
http://<gpudb.host>:9191/wms
?VERSION=1.1.1
&REQUEST=GetMap
&SRS=EPSG:4326
&WIDTH=1024
&HEIGHT=1024
&LAYERS=MASTER
&STYLES=raster
&TRANSPARENT=TRUE
The requested image will then be returned in the HTTP response message body.
The following parameters are required in all WMS calls:
| Name | Description | Notes |
|---|---|---|
| VERSION | WMS Version | Must be 1.1.1 |
| REQUEST | WMS Request |
|
| SRS | Spatial Reference System (i.e. EPSG code) |
|
| WIDTH | Image width | Best performance if width is a power of 2 |
| HEIGHT | Image height | Best performance if height is a power of 2 |
| LAYERS | The requested image layer(s) | One or more comma separated GPUdb GUIDs (i.e. table IDs) |
| STYLES | The style of image requested |
|
| TRANSPARENT | Controls background transparency of the generated image |
|
| FORMAT | Output image format | Must be image/png |
| BBOX | Geographic bounding box | min_longitude, min_latitude, max_longitude, max_latitude [Note that Google Earth adds this in automatically] |
The following parameters are optional for WMS calls:
| Name | Description | Notes |
|---|---|---|
| X_ATTR | Name of the attribute to be used as the longitude | Must be a numeric attribute in at least one of the sets. Defaults to x if omitted |
| Y_ATTR | Name of the attribute to be used as the latitude | Must be a numeric attribute in at least one of the sets. Defaults to y if omitted |
The following modes are supported:
Descriptions of each mode along with the mode-specific parameters can be found below.
The raster mode is used to rasterize points, shapes, symbols, and/or tracks from one or more GPUdb tables. Available parameters are:
| Name | Description | Allowable Values | Default Value |
|---|---|---|---|
| DOPOINTS | Rasterize point data toggle | TRUE or FALSE |
TRUE |
| DOSHAPES | Rasterize shapes toggle | TRUE or FALSE |
TRUE |
| DOSYMBOLOGY | Rasterize symbols toggle | TRUE or FALSE |
FALSE |
| DOTRACKS | Rasterize tracks | TRUE or FALSE |
TRUE |
| POINTSIZES | Size of points | 0-20 | 3 |
| POINTCOLORS | Color of points | Hex color | FF0000 (red) |
| POINTSHAPES | Shape of points |
|
|
| SHAPELINEWIDTHS | Line widths of shapes | 0-20 | 3 |
| SHAPELINECOLORS | Line colors for shapes | Hex color | FFFF00 (yellow) |
| SHAPEFILLCOLORS | Fill color for closed shapes (i.e. polygons) | Hex color (or -1 for no fill) |
-1 (no fill) |
| TRACKLINEWIDTHS | Line widths of tracks | 0-20 (0: don't draw the track lines) |
3 |
| TRACKLINECOLORS | Line colors for tracks | Hex color | 00FF00 (green) |
| TRACKMARKERSIZES | Size of track point markers | 0-20 | 2 |
| TRACKMARKERCOLORS | Color of track point markers | Hex color | 0000FF (blue) |
| TRACKMARKERSHAPES | Shape of track point markers |
|
none |
| TRACKHEADSIZES | Size of track head markers | 0-20 | 10 |
| TRACKHEADCOLORS | Color of track head markers | Hex color | FFFFFF (white) |
| TRACKHEADSHAPES | Shape of track head markers |
|
circle |
In addition, the WORLDLAYERS parameter can be used if the GPUdb table(s)
specified in the LAYERS parameter only have a subset of all track points and
the desired behavior is to render the entire track. In this case the unique
track ids existing in the LAYERS table(s) will be identified, but the actual
track points will be pulled from the WORLDLAYERS table(s).
Styling parameters must be specified for each GPUdb table provided in the
LAYERS parameter. For instance, if LAYERS=LAYER1,LAYER2 then to set
different point colors for each layer the syntax would be:
POINTCOLORS=FF0000,0000FF. In this case points from LAYER1 would be
rendered as red while points from LAYER2 would be rendered as blue.
All colors must be provided in hex notation in the format RRGGBB or
AARRGGBB (to specify the alpha value). For example, opaque red may be given
as FF0000 or FFFF0000.
If using symbology, then the type definition must include an attribute called
SYMBOLCODE which is the desired symbol's identifier. All necessary symbols
need to be added to GPUdb via the /insert/symbol endpoint.
The class break raster mode is for generating class break renderings. A
class break rendering is the rasterization of the data from one or more GPUdb
tables with styling applied on a per-class basis. GPUdb supports class breaks
based on one or more data attributes. Distinct values (for strings) or ranges
(for numeric attributes) must be provided in the CB_VALS/CB_VALS1 and
CB_VALS2 parameters. In addition to all of the RASTER mode parameters
the additional parameters for this mode are:
| Name | Description | Allowable Values |
|---|---|---|
| CB_ATTR or CB_ATTR1 | First class break attribute Required | Any valid attribute name |
| CB_VALS or CB_VALS1 | Values or ranges to apply for the class break Required | Comma separated list of values or ranges (e.g. 0:5,5:10,15:30) |
| CB_ATTR2 | List of second class break attributes Optional | Comma separated list of valid attribute names. An empty string implies not using more than one attribute for the class break. For a non-empty list, there needs to be as many entries in the list as there are classes for the first attribute. However, the attribute names can be empty to indicate that for the corresponding class of the first attribute, no secondary class break will be applied. All the attribute names in this list must be different from the first attribute (e.g. attr2,attr3,attr2). |
| CB_VALS2 | List of list of values/ranges to apply for the second class break NOTE: Required only if |
Comma separated list of []-enclosed lists of values or ranges (e.g. [0:5,5:10],[of,on,so],[-50:-20]). Each square bracket enclosed list describes the secondary classes for the respective attribute in CB_ATTR2 and the respective class in CB_VALS/CB_VALS1. |
All of the RASTER-mode styling parameters are valid for CB_RASTER;
however, there must be styling parameters specified for each class. If there is
a single class break attribute (i.e. CB_ATTR2 is not provided) then the
number of classes is the number of entries in CB_VALS/CB_VALS1. If there
are more than one class break attributes, then the number of total classes is
the sum of the entries (each value/range) in CB_VALS2.
For example, say we wish to render the data in the MY_SET GPUdb table
where string attribute named attr1 is equal to either DS1 or DS2, a
numeric attribute named x is between [-5,0] or [5,10] for
attr1==DS1, and another numeric attribute named y is between [0,42]
for attr1==DS2. CB_ATTR/CB_ATTR1 would be attr1, and
CB_VALS/CB_VALS1 would be DS1,DS2. CB_ATTR2 would be x,y,
and CB_VALS2 would be [-5:0,5:10],[0:42]. We could accomplish this via
the WMS request:
http://<gpudb.host>:9191/wms
?...
&LAYERS=MY_SET
&STYLES=cb_raster
&CB_ATTR1=attr1
&CB_VALS1=DS1,DS2
&CB_ATTR2=x%2Cy
&CB_VALS2=%5B-5%3A0%2C5%3A10%5D%2C%5B0%3A42%5D
&POINTCOLORS=FF0000,00FF00,0000FF
&...
In this case data from the set would be styled such that:
attr1=DS1 and x is in the range [-5,0] would have points rendered in red (FF0000)attr1=DS1 and x is in the range [5,10] would have points rendered in green (00FF00)attr1=DS2 and y is in the range [0,42] would have points rendered in blue (0000FF)The heatmap mode is used to generate a heat map image of one or more GPUdb tables. Heat maps show the density of data and use a color scheme to differentiate between low and high density areas. Available parameters are:
| Name | Description | Allowable Values | Default Value |
|---|---|---|---|
| BLUR_RADIUS | Blurring radius for the heat map | 1-32 | 5 |
| COLORMAP | Colormap for the heat map |
|
(none) |
| GRADIENT_START_COLOR | Gradient start color for the heat map | Hex color | FFFFFF (white) |
| GRADIENT_END_COLOR | Gradient end color for the heat map | Hex color | FF0000 (red) |
| VAL_ATTR | Attribute to use to calculate the density for the heat map | An existing attribute of the type definition | (none) |
If both COLORMAP and GRADIENT_START_COLOR/GRADIENT_END_COLOR are
provided then the COLORMAP is ignored and the user-provided
GRADIENT_START_COLOR/GRADIENT_END_COLOR are used as the color scheme. If
no VALUE_ATTR_NAME is specified, then the count of data points for any given
position will be used to generate the heatmap.
The cached mode is intended to be used in conjunction with the
/visualize/video and visualize_video_heatmap_rest endpoints.
Once one of those endpoints has been called, the generated video frames are
available for download via WMS using STYLES=cached. In this case, the
LAYERS parameter should be populated with the session key passed in to
/visualize/video or visualize_video_heatmap_rest and the
FRAME parameter indicates which 0-based frame of the video should be
returned. All other WMS parameters are ignored for this mode.
For instance, if a 20 frame video with the session key MY-SESSION-KEY was
generated with a call to /visualize/video, the first frame could be
retrieved with the URL:
http://<gpudb.host>:9191/wms
?REQUEST=GetMap
&STYLES=cached
&LAYERS=MY-SESSION-KEY
&FRAME=0
and the last frame could be retrieved with:
http://<gpudb.host>:9191/wms
?REQUEST=GetMap
&STYLES=cached
&LAYERS=MY-SESSION-KEY
&FRAME=19