GPS Comparisons Auto
How can I get spare parts for my Altimaster?
There are three ways to get spare Altimaster parts, including Neptune battery covers, Galaxy mounting screws, and more: If you have a mechanical Altimaster (Altimaster II, Altimaster III, or Altimaster III Galaxy), yes, this is normal. Most altimeters do NOT directly measure altitude, they measure barometric pressure. As you go higher in altitude the air pressure drops, and the altimeter mechanism reacts to the change in pressure by rotating the pointer.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.
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.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.
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 can I get spare parts for my Altimaster?
There are three ways to get spare Altimaster parts, including Neptune battery covers, Galaxy mounting screws, and more: If you have a mechanical Altimaster (Altimaster II, Altimaster III, or Altimaster III Galaxy), yes, this is normal. Most altimeters do NOT directly measure altitude, they measure barometric pressure. As you go higher in altitude the air pressure drops, and the altimeter mechanism reacts to the change in pressure by rotating the pointer.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.
How much power do the TX-units use?
Depending on the mAh rating of the batteries you use, and the update frequency you select you will get different run times. As well, the radio can be put into ‘serial sleep’ mode which lowers its power consumption when not transmitting down to 5 ma. Setting the Radio to ‘serial sleep’ does help conserve battery power for applications where the update time is 10 seconds or more.
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.
