FAQ About Creating Streaming Map Movies

Building Architectural Framework for Streaming Map Movies:

- Publishing streams through JMF libraries.
- Enhanced SMT with movie capabilities
- Easy to display movie streams
........... from Collaboration sessions
........... from standalone JMF client program

46. What is streaming map movie?
Visualizing changes over time is achieved by integrating temporal information on a map. Usually the result is a series of static maps showing certain themes at different moments. In addition to creating static maps, WMS also has the ability to combine the static maps correspond to a specific time interval data and combine them in an animated movie. Movies created by WMS are composed of a certain number of frames. Each frame represents a static map that corresponds to a time frame defined in request.

47. Why do you need to create map movie?
Standard map servers produce static images, but many types of geographic data are time dependent. In order to understand geographic phenomena and characteristics of temporal data it is necessary to examine how these patterns change over time for these types of data.

48. How does WMS create a streaming map movie?
Movies in general are composed on static frames. Frames are actually images. Movies are obtained by playing these static frames sequentially. In our case of map movies, frames are static map images created for a specific bounding box and a specific time interval. Sequential frames are created based on successive time intervals. Range of interval is given by the client from the user interface. See below figure, time interval is set to “P1Y”.

In order to get better view of the figure, please click on it.

Movies are created just for time-dependent data. WMS notify the clients for what layers it can create movie streams through its capabilities file. If a client makes a request to get a movie for a specific layer, to succeed, this layer should have a time dimension defined under this layer element in the capabilities file. Here is an example dimension tag under the layer tag in capability. Layer is created based on a data which is provided yearly.

In order to get better view of the figure, please click on it.

The last value “P1Y” (in the Dimension tag element above) defines the periodicity of the data collection. According to this value, WMS cuts the whole time (“from/to/periodicity”) into multiple values and for each time slice, it makes a "getFeature” request to WFS to get feature data in GML. After receiving GML, WMS creates static map images for each time slice. These images will be frames of the result map movie.
Clients should make the “getMap” standard request to WMS to get the movie for a specific layer but the “format” variable should be set to “movie/ ” and “time” variable should be set to a value in an appropriate format. The last value in the Dimension tag element (P1Y) is defined based on the user’s selection from the drop-down list shown in above figure. (See also a sample request for the movie in Q49 below).
Below figure is the BIG PICTURE for the creation of the map movies. In order to get further information for the map movies please see the *draft* technical report
http://complexity.ucs.indiana.edu/~asayar/gisgrids/docs/movie_jmf.doc.

In order to get better view of the figure, please click on it.

49. Can you give a sample movie request sent to WMS?
The request is actually “getMap” request with specific parameters set to specific values. We might need to request a map movie based on the layer created from a data. WMS defines this layer in its capabilities file with the “dimension” tag as displayed in Q48. In order for WMS to create map movie we need to send a “getMap” request as below. Here we request an mpeg movie created from frames created with a yearly data. First frame starts with the year 1987 and last frame ends with the year 1992. So, movie will be created from five frames.

In order to get better view of the figure, please click on it.

50. Can you define any attributes such as frame rate for the movie streams published by WMS?
The map video stream has several parameters that can be adjusted. These parameters affect the quality of the produced map video stream. Among these configurable parameters are frame rate and video format of the stream, update rate of the map images in the video stream.
In our current implementation, we define these attributes in hard coding but in the future we will take it from the smart map tools interface. This is necessary because; some clients might not be capable of visualizing video streams with low frame rate or can visualize them with very low quality because of their connection or some other issues. They might need to adjust the attributes and get the best result.

51. How do you display map videos?
When the frames (static maps) corresponding to separate time slices are created, WMS publishes them to a Real Time Protocol (RTP) session as streams. RTP sessions are defined with IP Address and Port Number couples. Movie streams published to an RTP session can be visualized by any client connecting to the same RTP session (same IP and port number defined by the publisher).
If you want to display the movie streams with a standalone program (not in collaboration environment such as AccessGrid and Global MMCS), then download and install JMStudio software (http://java.sun.com/products/java-media/jmf/). From the user interface select “File” menu and click on “open RTP session” and give IP, port and time to live (ttl) values that you already know there is one WMS publishing map movie streams to this session.

52. Do you have any sample map movie to see online?
Yes, see the below link. Movie at the below link is obtained by screen recording of the real PI Geo-Science application’s output. Movie is composed of yearly seismic earthquake records. The minimum magnitude is 4.0 (PI spec parameter), and frames are composed of static maps created yearly based.http://complexity.ucs.indiana.edu/~asayar/gisgrids/html/work/AutoScreenRecorder_01.mpg