What type of altitude input is required for TAWS?
Most TAWS installations require only uncorrected barometric pressure altitude information from an existing encoding altimeter. This altitude information is combined together with the altitude dervied from the connected GPS to provide accurate altitude information. This combination of pressure altitude and GPS altitude is called “Geometric Altitude” which is less susceptible to errors or malfunctions from normal altimeter systems.
Why have a barometric altimeter?
Quite simply, the primary reason you would want a barometric altimeter in a handheld GPS is for more accurate elevation readings. This is especially useful for bikers, hikers and atheletes in training. You can use the resulting data to track your progress and maintain an accurate record of your trips. A barometric altimeter can also help you accurately place your location on a topo map. Furthermore, you can use the altimeter to forecast weather on the mAh rating of the batteries you use, and the update frequency you select you will get different run times.
Is the GPS Altitude Accurate?
Now that SA (Selective Availability) has been turned off, the general answer to this is Yes. GPS altitude is at least as accurate as the reading from a barometric altimeter. However, to determine altitude a GPS MUST be receiving information from at least three satellites and the more it is tracking, the better. If you want more information on this subject, there have been NUMEROUS postings on the rec.aviation.soaring and sci.geo.satellite-nav newsgroups. I encourage you to check them out.
When starting FsXPand, I am unable to taxi away. What is happening?
There was a bug in version 4.3 causing the parking brakes to lock. If this behaviour is still present in version 5.1, please check if you have assigned brakes to a analog channel and wired it up reversely (a common error). You should be able to taxi when the brakes are fully down. Reverse the wiring in that case.
When starting FsXPand, I am unable to taxi away. What is happening?
There was a bug in version 4.3 causing the parking brakes to lock. If this behaviour is still present in version 5.1, please check if you have assigned brakes to a analog channel and wired it up reversely (a common error). You should be able to taxi when the brakes are fully down. Reverse the wiring in that case. After resizing the panel, the tics in my fuel gauges are gone, and there are no digits anymore. There is a bug causing this to disappear.Now that SA (Selective Availability) has been turned off, the general answer to this is Yes. GPS altitude is at least as accurate as the reading from a barometric altimeter. However, to determine altitude a GPS MUST be receiving information from at least three satellites and the more it is tracking, the better. If you want more information on this subject, there have been NUMEROUS postings on the rec.aviation.soaring and sci.geo.
How is the altitude reported by the pressure sensor calculated?
The altitude calculated from the pressure sensor readings is based on the U.S. Standard Atmosphere (1976). A lookup table contained within the AFC-877’s onboard firmware is used to find the calculated altitude based on the pressure value read. When the altimeter reports the peak barometric altitude, or when a low altitude event occurs, the altitude value used is based on this standard. The on the mAh rating of the batteries you use, and the update frequency you select you will get different run times.