A. Charles Branch

Charles Branch is a GIS marketing manager at Ashtech Inc. in Sunnyvale, Calif.He may be reached at 408-524-1603 (phone), 408-524-1500 (fax), or e-mail: cbranch@ashtech.com Tom Damiani is manager, key programs marketing in the Wireless Communications Division at Rockwell Semiconductor Systems in Newport Beach, Calif.He may be reached at 800-854-8099 (toll free phone) or e-mail: literature@hb.rockwell.com Dr. Frank van Diggelen is a marketing manager, OEM and Navigation at Ashtech Inc. in Sunnyvale, Calif.He may be reached at 408-524-1508 (phone), 408-524-1500 (fax), or e-mail: frank@ashtech.com Chuck Gilbert is an applications engineer at Trimble Navigation in Sunnyvale, Calif.He may be reached at 408-481-8000 (phone), 408-481-6074 (fax), or e-mail: chuck gilbert@trimble.com Naush Ladha is an applications engineer in NovAtel GPSs Sales and Marketing Division, headquartered in Calgary, Alberta, Canada.Ladha may be reached at 403-295-4564 (phone), 403-295-4901 (fax), or e-mail: nladha@novatel.com

Charles Branch, Ashtech: For the purpose of GPS surveying, a datum is a set of constants specifying the coordinate system used for calculating coordinates of points on the Earth.There are eight constants that define a datum: three to specify the location of the origin of the coordinate system, three to specify the orientation of the coordinate system, and two to specify the dimensions of the reference ellipsoid. A comparison to a locally defined coordinate system commonly used in surveying may help clarify.Commonly, a local coordinate system may be defined for a small project by randomly defining a point close by as the origin.This could be a boundary point of a land parcel.Coordinates are assigned to this point such as 0, 0 or 500, 500.In contrast, the origin of a datum is often, but not always, defined as the center of the Earth (termed a geocentric datum), where the coordinates are 0, 0, 0.
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Branch: The easiest way is to use a laser range finder (LRF) and a compass.You first lase the feature of interest and determine its range from where you are standing.You then determine the azimuth to the feature using the compass.You then combine these two measurements with your GPS position and compute the position of the feature. The more this can be automated, the easier this task is.You can buy LRFs with built-in electronic compasses.These go quite a way toward automating the process.
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Charles Branch is a GIS marketing manager at Ashtech in Sunnyvale, Calif.He may be reached at 408-524-1400 (phone), 408-524-1500 (fax), or e-mail: cbranch@ashtech.com

Charles Branch , Ashtech : For the purpose of GPS surveying , a datum is a set of constants specifying the coordinate system used for calculating coordinates of points on the Earth.There are eight constants that define a datum : three to specify the location of the origin of the coordinate system , three to specify the orientation of the coordinate system , and two to specify the dimensions of the reference ellipsoid.A comparison to a locally defined coordinate system commonly used in surveying may help clarify.Commonly , a local coordinate system may be defined for a small project by randomly defining a point close by as the origin.This could be a boundary point of a land parcel.Coordinates are assigned to this point such as 0 , 0 or 500 , 500.In contrast , the origin of a datum is often , but not always , defined as the center of the Earth ( termed a geocentric datum ) , where the coordinates are 0 , 0 , 0. Next , in the local system , a direction is defined in order to orient the two axes of the coordinate system.
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Branch : The easiest way is to use a laser range finder ( LRF ) and a compass.You first lase the feature of interest and determine its range from where you are standing.You then determine the azimuth to the feature using the compass.You then combine these two measurements with your GPS position and compute the position of the feature.The more this can be automated , the easier this task is.You can buy LRFs with built-in electronic compasses.These go quite a way toward automating the process.
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Charles Branch is a GIS marketing manager at Ashtech in Sunnyvale , Calif..He may be reached at 408-524-1400 ( phone ) , 408-524-1500 ( fax ) , or e-mail : cbranch@ashtech.com.

A. Charles Branch , Ashtech Inc. : Simple answer : MaybeMore complete answer : This wont yield the accuracies of more sophisticated methods of differential correction.Also , if using this method , you really should calculate both base and rover positions using the same GPS satellites at the same time.This is hard to do.If you dont do this , your corrections will be unpredictable and could fail to improve accuracy at all.You could get 5 meters of accuracy or you could get 100 meters.You may be more satisfied buying a software solution from a GPS manufacturer.
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Charles Branch is a GIS marketing manager at Ashtech Inc. in Sunnyvale , Calif..He may be reached at 408-524-1603 ( phone ) , 408-524-1500 ( fax ) , or e-mail : cbranch@ashtech.com Tom Damiani is manager , key programs marketing in the Wireless Communications Division at Rockwell Semiconductor Systems in Newport Beach , Calif..He may be reached at 800-854-8099 ( toll free phone ) or e-mail : literature@hb.rockwell.com Dr. Frank van Diggelen is a marketing manager , OEM and Navigation at Ashtech Inc. in Sunnyvale , Calif..He may be reached at 408-524-1508 ( phone ) , 408-524-1500 ( fax ) , or e-mail : frank@ashtech.com Chuck Gilbert is an applications engineer at Trimble Navigation in Sunnyvale , Calif..He may be reached at 408-481-8000 ( phone ) , 408-481-6074 ( fax ) , or e-mail : chuck gilbert@trimble.com Naush Ladha is an applications engineer in NovAtel GPSs Sales and Marketing Division , headquartered in Calgary , Alberta , Canada.Ladha may be reached at 403-295-4564 ( phone ) , 403-295-4901 ( fax ) , or e-mail : nladha@novatel.com.

Branch: The easiest way is to use a laser range finder (LRF) and

a compass.
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Charles Branch is a GIS marketing manager at Ashtech in Sunnyvale,

Calif.He may be reached at 408-524-1400 (phone), 408-524-1500 (fax),

Charles Branch is a GIS marketing manager at Ashtech

Inc. in Sunnyvale, Calif.He may be reached at 408-524-1603 (phone), 408-524-1500

Charles Branch is a GIS marketing manager at Ashtech Inc. in Sunnyvale, Calif.