Ashtech MobileMapper 10 Specifikace stáhnout pdf (Strana 42)

English

Coordinate Systems

When creating a new DXF job or when creating a layer as the

first layer in a new *.map job, MobileMapper Field asks you

to define a coordinate system.

Choosing a

Coordinate System

Proceed in this order:

1. Choose the World Geodetic System or the country where

your field operations will take place

2. In the field just underneath, choose the datum used

3. In the field just underneath, choose the projection used.

4. Choose the vertical datum in the last field. The default

possible choices are:

– Ellipsoid: Each altitude or height value is simply

determined with respect to the selected ellipsoid

(second field above).

– EGM84: Each altitude or height value is still initially

determined with respect to the selected ellipsoid but a

correction is applied to that value. The correction is

read from the EGM84 geoid (Earth Geoid Model 1984,

a global geoid model) and is specific to the computed

horizontal position.

Other geoid models may be downloaded to the receiver via

the MobileMapper Software CD from the Ashtech website.

Once downloaded, they are made available as possible

choices in the Vertical Datum field.

The Properties... button at the bottom of the screen allows you

to view the properties of the selected datum and projection.

The New... button at the bottom of the screen allows you to

create a user system (datum + projection).

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Ashtech MobileMapper 10 Specifikace Strana 42