See Also
 Important: |
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| This is retired content. This content is outdated and is no longer being maintained. It is provided as a courtesy for individuals who are still using these technologies. This content may contain URLs that were valid when originally published, but now link to sites or pages that no longer exist. |
This IOCTL can be implemented by GPS hardware manufacturers to obtain almanac information previously saved by an application using IOCTL_GPS_READ_ALMANAC. This data may provide enough information to the GPS hardware to enable the hardware to obtain a GPS fix more quickly than it would without almanac data.
An application can use this IOCTL to provide information it previously retrieved, using IOCTL_GPS_READ_ALMANAC.
For more information about how to use and implement this IOCTL, see Implementing GPS Intermediate Driver Hardware IOCTLs.
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| Non-almanac data that can be used to enable faster GPS fixes - like mobile phone tower information, for example - should be provided using IOCTL_GPS_WRITE_ASSISTED. |
Parameters
Applications using the GPS Intermediate Driver should use the lpInBuffer parameter of the DeviceIOControlfunction to pass a pointer to a buffer that contains data previously retrieved using IOCTL_GPS_READ_ALMANAC.
GPS hardware manufacturers that implement this IOCTL can use the lpInBuffer data to attempt to make a GPS fix more quickly.
It is important to note that the almanac data is only meaningful to the GPS hardware. The data is completely opaque to an application using the GPS Intermediate Driver. The degree to which applications can interact with almanac information is limited to saving the results of IOCTL_GPS_READ_ALMANACand then providing the saved results to the GPS hardware using IOCTL_GPS_WRITE_ALMANAC.
Return Values
GPS hardware manufacturers may return TRUE if the hardware device driver was able to use almanac data for initialization, and FALSE otherwise. However, this is not required and applications should not rely on the return value obtained when using this IOCTL.
Requirements
| Header | gpsdev.h |
| Windows Embedded CE | Windows Embedded CE 6.0 and later |
| Windows Mobile | Windows Mobile Version 5.0 and later |