Friday, October 24, 2008

GPS Comparisons Auto

By Hodges Rios

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 trends.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.

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.

How accurate are the heights or depths?
The aircraft vertical position was determined using the navigational positioning equipment on the aircraft, which were radar altimeter and barometric altimeter. Radar altimeters are estimated to have an error of 2-5% of the altitude (Richard Hansen, PRJ, Inc., written communication). Barometric altimeters are quite accurate, but are typically operated in an uncorrected mode.During that time you experienced your max Uphill Grade, Max Ascent and Descent Rate.

How accurate are the heights or depths?
The aircraft vertical position was determined using the navigational positioning equipment on the aircraft, which were radar altimeter and barometric altimeter. Radar altimeters are estimated to have an error of 2-5% of the altitude (Richard Hansen, PRJ, Inc., written communication). Barometric altimeters are quite accurate, but are typically operated in an uncorrected mode.The aircraft vertical position was determined using the navigational positioning equipment on the aircraft, which were radar altimeter and barometric altimeter. Radar altimeters are estimated to have an error of 2-5% of the altitude (Richard Hansen, PRJ, Inc., written communication). Barometric altimeters are quite accurate, but are typically operated in an uncorrected mode.

How accurate are the heights or depths?
The aircraft vertical position was determined using the navigational positioning equipment on the aircraft, which were radar altimeter and barometric altimeter. Radar altimeters are estimated to have an error of 2-5% of the altitude (Richard Hansen, PRJ, Inc., written communication). Barometric altimeters are quite accurate, but are typically operated in an uncorrected mode.Some high-end GPS devices offer barometric pressure to obtain a measurement for elevation when signal reception is not very good. The result is that you will have a smoother elevation profile in the Dashboard and Map Player. Without an altimeter, the GPS assumes your elevation is not changing when the signal goes bad. This results in a blocky elevation profile. - 15478

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