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Chapter 3: Cartography and Basic Geodesy

MAPS

AND

CARTOGRAPHY



What is a MAP?

- helps to extend our normal range of vision

- use to portray the world around us

- use to portray information about the earth’s surface


AERIAL PHOTOGRAPH


Aerial photos from the second worldwar (near Germany)


THEMATIC MAPSAMPLE MARIJUANA GROWTH DATA


WHAT IS A THEMATIC MAP?

• Thematic maps can cover a variety of characteristics from soil types to popu la t ion dens i ty . I t i s the cartographers responsibility to make sure that the map shows the correct distribution or the relationship between the various attributes.


WHEN DO WE USE THEMATIC MAPS?

• Thematic maps can show not only the distribution of a single attribute, such as the result of a presidential election by state, but they can also show the relationship between several different attributes. For instance, a thematic map could show the results of that same presidential election with the number of votes divided according to the gender or age group of the voters.


WHAT MAKES A GOOD THEMATIC

MAP?


PLANIMETRIC MAP


What is Planimetric map?

• A map designed to portray the horizontal positions of features; vertical information is specifically ignored.

• Sometimes called a line map. It shows line drawings of ground features.

http://en.mimi.hu/gis/map.html


• Planimetric maps describe the world as if it were a flat surface. They typically show basic details like main trails, lakes and campsites.

• Use a planimetric map only when traveling short distances along well- established trails.


TOPOGRAPHIC MAP


Topographic maps

• Topographic maps describe the physical features of the land. They show elevation gains and losses, the steepness of hills and valleys, and the location of natural features. This topographic information is essential for navigating using a map and compass. Some topographic maps (but not all) combine topographic information with basic information about trails, campsites and natural attractions. The main supplier of topographic maps in the US is the United States Geological Survey (USGS).


COMPUTER-GENERATED MAP


• Can be manipulated• Is easy to update• Can be viewed in different angles• GIS produces outputs like this • Colors can sometimes be misleading• Features may be fake!• Essential for future spatial planning.


Orthophoto Map


• The ortho process corrects for distortions caused by the terrain, the orientation of the airplane and the camera lens. Orthorectification results in a planimetric image that allows users to accurately measure distances and areas.

• In the simplest terms, an ortho image is like a photo that has been draped over the ground like spreading a blanket over an uneven surface. The ground is represented by an elevation model. Orthophotography is a product which has the geometric accuracy of a map but contains the immense detail of a photograph.

• Since the development of the G.I.S., orthophoto have been primarily developed for use in a digital environment. A digital orthophotograph is a photo-quality digital image (a raster image) of surface features in their geometrically-corrected, true map position. The popularity of digital orthophotography is growing fast with the advent of more powerful computers and software.


BASIC MAP COMPONENTS

1. North Arrow

2. Map Title

3. Map Scale

4. Map Symbols

a. Point Symbolb. Line Symbolc. Area Symbol

5. Notes and Legends


NORTH ARROWS


S Y M B O L S F O R V E G E T A T I O N

S Y M B O L S F O R V A R I O U S F E A T U R E S

S Y M B O L S F O R B O D I E S O F W A T E R



Choose the Right Scale• The scale of a topographic map determines how much land the

map covers and how much detail it provides. Scales are described in ratios (1:24,000, for example, means that one inch on the map is equal to 24,000 inches -or 2,000 feet- on the ground). The scale of a map is usually displayed along the bottom edge of the map.

• Small-scale maps maps with smaller scales cover a lot of area, but they provide less detail as a result. They tend to be a poor choice for beginning backpackers.

• Large-scale maps focus on more specific areas and provide more detail. You may have to carry more than one to cover your route. But they provide much more useful information for basic backpacking.


BASICGEODESY


Different Shape, Different Position


GEODESY DEFINED

- Is the study of the shape and size of the earth in the geometrical sense.

- Study of certain physical phenomena, such as gravity, in seeking explanation of fine irregularities in the earth’s shape.


THREE OBSERVATIONS WHY THE EARTH IS NOT FLAT

1st OBSERVATION


2ND OBSERVATION

3RD OBSERVATION


THE SHAPE OF THE EARTH

- SPHERICAL EARTH

- ELLIPSOIDAL EARTH

- GEOIDAL EARTH


GEOID - ELLIPSOID RELATIONSHIPS

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