Cartography and Geomatics. Map Basics

Transcription

1 Cartography and Geomatics Cartography: The art, science and technology of making maps Map: A two dimensional scaled representation of a planetary surface ( traditional definition) - includes online displays, animations Geomatics: An umbrella term for the mapping technologies (managing spatial data) Map Basics The nature of mapping Uses and purpose of maps and spatial data Types of maps and data Map and data layers Mapping Scales 1

2 1a. Mapping is never finished (for us) 1b. There are multiple map products for the same area 2

3 General uses / purpose of Maps & Spatial data A. Display and store of spatial information (space) B. Historical record of spatial features (time) General use/purpose of Maps & Spatial data A. Display and store of spatial information B. Historical record of spatial features Kakwa Park, BC (google maps) 3

4 Map purpose: C. Communication tool Map purpose: C. Communication tool Library books borrowed by country - cartogram Example: 4

5 General Uses of Maps & Spatial data C: Communication tool e.g. propaganda German map, world war II General Use/purpose of Maps & Spatial data D. Vicarious travel 5

6 D. Vicarious travel (or a work of art) E. Maps as a work of art 6

7 Maps as a work of art? Types of Maps and data There are traditionally two main types of map and data categories: a. General purpose (topographic) These show the visible features of the landscape e.g. relief, water bodies, and roads - base maps, relief maps, city maps. 7

8 Types of Maps and data b. Special purpose (thematic) Emphasis is placed on a particular element e.g. climate, geology, population density, industry. Global coffee consumption 8

9 Summary Map purpose (use) This is the preliminary question in map design/production 1. Function spatial display, historical, communication, artistic 2. General topographic or thematic or mixture 3. Specific what is this map for? Map and data layers Maps and databases are composed of layers or themes feature types are organised in layers e.g. containing roads, rivers etc.. There are three types (vectors): points, lines and areas (polygons) 9

10 Raster (grid) layers In addition to the 3 feature types, there are continuous grids (rasters) e.g. for air photos, images, relief models Spatial data: location and attributes Map layers encode two different types of information: a. Spatial location (where is it?) b. Attributes (what is it?).. In GIS software, these data are stored in a single layer (but with multiple files) e.g. Roads as a shapefile roads.shp roads.dbf roads.shx This differs from mapping / non-gis software 10

11 Map Scales Scale represents the reduction compared to the distances on the earth's surface. Without a scale, it is a diagram, (not a map) Scale can be given in 3 ways: a. Verbal statement For example, 1 cm to 10 km, 1 inch to 1 mile Verbal statements are simple to understand They are unit-dependent b. Scale bar Graphic, units are stated e.g. kilometres or miles The left end of the bar can be subdivided in smaller units for easier estimation of precise distances. This practice is only appropriate for topographic maps. This is widely abused with GIS software Topographic Thematic Classic traditional scale bars 11

12 c. Ratio or representative fraction (RF) This states the reduction as a fraction or ratio (e.g. 1:100,000 or 1/100,000 ) It is free of specific units (metric or imperial) It can describe map series and datasets (e.g. 1:50,000) 1:20,000 is a larger scale than 1:50,000 (1/20,000 IS bigger than 1/50,000) Conversion between a statement and a representative fraction Get each side of the scale into same units, for example: To convert 1 cm to 1 km into a ratio: 1 km = 1000m = 100,000 cm So 1cm to 1km is the same as 1:100,000 To convert 1:250,000 to a statement: 1 cm to 250,000 cm = 2500m = 2.5 km Scale is 1 cm to 2.5 km More: 12

13 common world scales / metric map series 1:1,000,000 (world) Small 1:500, :250,000 Medium (1:125,000) :50,000 Large 1:20,000 (provincial) :10,000 (cadastral) Very large common world scales / imperial series Canada converted to metric post world war II 1:506,880 1 = 8 miles -> 1:500, : 253,440 1 = 4 miles -> 1: 250,000 1: 126,720 1 = 2 miles -> 1:125, : 63,360 1 = 1 mile -> 1:50,000 13

14 Summary: 3 ways of showing scale: the graphic is best on a final map 1: 16,000,000 1: 1,300,000 14