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U.S. National Grid for Beginners�(Part 2 – How to Use USNG With a U.S. Topographic Map)

105

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Review and relevance: Map Accuracy

- National Map Accuracy Standard (NMAS)

- NMAS = >1:20,000 = 90% of well defined features will be within 1/50 inch on map of true position.

@ 1:24,000, 90% of well defined mapped features will be within 12.19-m of true position on the ground.

- @ 1:24,000, 12-m = 0.5-mm...

...or dot from 0.5-mm pencil lead =

- USGS 1:24,000 series topo maps = NMAS.

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In other words...

matches GPS...

…in accuracy.

It is worth noting, this accuracy was achieved at no trivial cost to the US Treasury over the last century.

The lessons: 1) Do not point at position with your finger.

2) Attention to detail when working.

Attention to detail when working.

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ppt

Building at grid:

145 100

Ex 1

Read right, and up.

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ppt

Building at grid:

1282 1122

Ex 1

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ppt

Road Intersection

at grid: 1318 0978

Ex 3

Read right, and up.

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ppt

Reconstructing

a grid

³³08

Road Intersection

at grid: 1425 0875

Ex 6

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ppt

Reconstructing

a grid

Building at grid:

1028 0976

Ex 8

²10

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ppt

Building at grid:

1215 0924

Ex 5