Garmin 23 Owner's Manual And Reference Manual

Also see for GA 23: Specifications

Contents

Garmin 23 Owner's Manual And Reference Manual Manual pdf 18 page image

16ReferenceSources ofErrorNumber of Satellites Visible— As previouslystated, the number of satellites available can affectposition accuracy. To apply the corrections provided forthe satellites received at the beacon transmitter station, thesame satellites (at least in part) must be received by yourGPS receiver. And, certainly, if there aren’t enoughsatellites to determine a GPS position, there aren’t enoughsatellites to calculate a DGPS position.Atmospheric Conditions— Differences in theionosphere and/or troposphere between the DGPSbroadcast station and the DGPS receiver can result indecreased position accuracy. Although this does not causesignificant error, the amount of error can increase as youget further away from the DGPS broadcast station.Satellite Geometry— A minimum of 4 satellites arerequired to determine a 3D position. At times, additionalsatellites are required due to their placement with respectto each other. This relative placement is referred to as“satellite geometry”. Ideal satellite geometry exists whenthe satellites are located at wide angles with respect toeach other. When satellites are located in a line, satellitegeometry is considered poor.This same requirement applies to DGPS. Ifcorrections are available for four different satellites, butthey are all located in the same general area or in a line,the DGPS corrections will be minimal. However, if thesame four satellites are placed farther apart, in several verydifferent directions from our position, the corrections willhave a much greater effect and the position accuracy willbe greatly improved.