GeoTechnology

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Symbols occupy more space than they generally take up based on the scale

Linear widths, sometimes rivers are lines on a map other times they are polygons (question of scale and what is the real width of the river)

Same is true for roads 

A plane that passes through the center of the Earth

For reference in projection terms a meridian passes through the poles

Since all are equal a prime meridian had to be selected

Longitude lines of the Earth’s graticule 

Lines placed at right angles to the meridians

The equator is a parallel and is the main reference point for projections

Latitude lines of the Earth’s graticule 

Global systems

– Most commonly used latitude and longitude

• • Reno, NV
• – Latitude 39° 30’ 30” North
• – Longitude -119° 48’ 30” West

• Degrees, Minutes, Seconds (dms)

• • Decimal Degrees (dd)
• – Latitude 39.508333333
• – Longitude -119.80833333

• • Conversion to decimal degrees
• – decimal deg. = degrees + (minutes / 60) + (seconds / 3600) 

A three-dimensional shape obtained by rotating an ellipse about its minor axis, with dimensions that either approximate the earth as a whole, or with a part that approximates the corresponding portion of the geoid.

The shape and size of a coordinate system is defined by the spheroid

Smaller scale systems can assume sphere shape for earth (more on that later) 

Most created with a specific region in mind

Earth not a true ellipse or sphere, but has an irregular shape. This shape is called a geoid.

Think in terms of the highest mountain peak and the lowest ocean valley

• Albers equal-area
• Conical can also be good for distances
• Scale and shape distorted 
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• Distortion different close to poles    
• Meridians are now the important points
• UTM zones run north-south with a central meridian 

• Projections onto a plane
• Good for direction
• Map distances can be computed by a function
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