AAPG

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First, many maps do not contain enough coordinate ticks or grid lines to scale and orient the map. ... locations) are used by surveyors and map makers throughout the world. ...

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AAPG

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Slide 1:AAPG Map Publication Standards

Purpose: To insure that features on published maps can be accurately located and that maps and imagery may be digitally merged.

Slide 2:So, what’s the problem?

First, many maps do not contain enough coordinate ticks or grid lines to scale and orient the map. Second, rarely is there a good enough description of the map parameters to uniquely reproduce the map.

Slide 3:Technical Issues:

Datums Map Projections Grid Coordinates

Slide 4:Datums:

Most longitude and latitude values are tied to ground surveying. These points not generally on the same datum (reference frame) as GPS locations. (The same point can have more than one correct longitude and latitude.)

Slide 5:Map Projections:

Maps are systematic representations of a round earth on flat paper, and as such cannot be equal scale everywhere. The map projection and the projection origin describe how the scale varies.

Slide 6:Grid Coordinates:

Hundreds of local coordinate systems (x and y locations) are used by surveyors and map makers throughout the world. Each is keyed to a specific projection and has a specific origin. UTM Zone 15N

Slide 7:Proposed Standards

Published maps should include a graphic scale and a north arrow. The accompanying text, or title block, should provide enough information to allow georeferencing. The information should include:

1) Projection type, and projection parameters (unless it is a common, documented projection). 2) Scale at projection origin. 3) Internal or marginal ticks or grid labeled with coordinate or grid values. 4) If X,Y coordinates (other than UTM or State Plane) are used, grid origin, false Easting and Northing, and units of measure. 5) Geodetic datum. Note that a few grid and projection types are well enough known that "NAD-27, Texas State Plane, Central Zone" or "Europe50, UTM, zone 32" are sufficient to completely characterize the map projections.

Slide 10:Exceptions

Index or location maps that contain no significant scientific information. 2) Maps reproduced from earlier publications for which no reliable projection information is available. 3) Sketch maps (generally they should include a north arrow and scale). 4) Mine maps (generally a north arrow, scale bar and local grid if available). 5) Global maps (projection type is generally all that is necessary to reproduce the map).

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