This topic explains how to transform coordinates so that an area displays properly on the Spatial Management Client.
Usually the map on the Spatial Management Client relates to the coordinate system of the event provider (hub) in such a way that the logical 0.0 point is either in the bottom left or top left corner (abstracting from the offset). In those cases it would be sufficient to define a scaling factor when defining the area and X and Y offsets. If your default 0.0 is in the top left corner and you want to change it to the bottom left, specify cartesian when defining the area.
The detailed information in this topic is necessary for more complex situations, where one hub is related to different maps with various orientation, overlap, and so on.
The following figure shows a simple scenario that demonstrates why at least one coordinate transformation is required in almost all cases.
The point has coordinates 20, 20 in the location event provider coordinate system. These coordinates must be translated to Spatial Management Client coordinates which are 7, 21 in this sample. Depending on the complexity of the setup, separate logical reference systems might be needed. In many cases, such as in the sample illustrated here, a system defined by the location event provider or the Spatial Management Client can be used as a reference system. In some setups, the systems might even be identical.
When the systems are identical, no coordinate transformation is needed. If either system acts as a reference system, one coordinate transformation must be made. If there is a separate reference system, two transformations must be made: one between the location event provider and the Location Awareness Services for WebSphere Premises Server server and one between the Location Awareness Services for WebSphere Premises Server server and the Spatial Management Client.
The transformations apply only to the X and Y coordinates. There is no need for three dimensional transformations because all components can be configured so that the Z-axis of their coordinate systems points upward.
The following samples show the effects that different values have.
As a consequence, areas must be aligned with either the location event provider's coordinate system or the intermediate reference system.
The following figures show the different location event provider and area configurations that can occur. The location event provider-defined coordinate system is depicted in light gray and the coordinate system defined in the Spatial Management Client for the area is in blue.
Scenarios A and B depict a single location event provider configuration and scenario C depicts a configuration where all location event providers refer to the same coordinate system.
In scenarios C and D, the X and Y axes of all areas must be aligned. In other words, the X axis of each area must point in the same direction and the Y axis of each area must point in the same direction.
Case | Location event providers | Area | Reference system | Comment |
---|---|---|---|---|
A | 1 | 1 | Location event provider or Spatial Management Client | When the Spatial Management Client is used frequently by multiple users, use the GUI's coordinate system as the reference. In all other cases, use the location event provider's coordinate system to reduce the number of transformations. |
B | None | 1 | Spatial Management Client | |
C | 1 | None | Location event provider | |
D | None | Multiple | Separate reference system | The separate coordinate system can coincide with the coordinate system of the location event provider, the Spatial Management Client, or both. |
In scenarios A, B, and C, a separate reference system can also be used. However, doing so increases the number of required transformations.
The following figures show some basic transformation scenarios. The original coordinate system is labeled with a "1", such as X-1, Y-1. The target system is labeled with a "2", such as X-2, Y-2. The scaling factor depends on the base units of both systems. The configuration settings are shown in the tables.
Configuration setting | Value |
---|---|
Rotation | 0 |
X-Y permutation | No |
X-offset | dx |
Y-offset | dy |
Configuration setting | Value |
---|---|
Rotation | 0 |
X-Y permutation | Yes |
X-offset | dy |
Y-offset | dx |
Configuration setting | Value |
---|---|
Rotation | 90 |
X-Y permutation | No |
X-offset | dx |
Y-offset | dy |
Configuration setting | Value |
---|---|
Rotation | 90 |
X-Y permutation | Yes |
X-offset | dy |
Y-offset | dx |
Configuration setting | Value |
---|---|
Rotation | 180 |
X-Y permutation | No |
X-offset | dx |
Y-offset | dy |
Configuration setting | Value |
---|---|
Rotation | 180 |
X-Y permutation | Yes |
X-offset | dy |
Y-offset | dx |
Configuration setting | Value |
---|---|
Rotation | 270 |
X-Y permutation | No |
X-offset | dx |
Y-offset | dy |
Configuration setting | Value |
---|---|
Rotation | 270 |
X-Y permutation | Yes |
X-offset | dy |
Y-offset | dx |
The transformation shown in the last sample occurs frequently in Location Awareness Services for WebSphere Premises Server configurations. The target coordinate system is like that defined by the Spatial Management Client, with the point of origin in the upper-left corner, with the Y axis pointing downward, and the X axis pointing to the right.