1. Data query can be applied for a) vector data b) raster data c) none of the ab
ID: 292882 • Letter: 1
Question
1. Data query can be applied for
a) vector data
b) raster data
c) none of the above
d) both a and b
2. You are given a map where the data have been classified into 3 classes. These classes are represented by circles, and the size of each circle is propportional to data value. This map type uses:
a) Dot density
b) Proportional symbols
c) Graduated symbols
d) Choropleth symbols
3. If you change the map projection of a data set, and then save that data in the new projection, and repeat this over and over, you are going to introduce errors into the data set because of:
a) changes in distortion
b) rounding errors
c) scale incompatibilities
d) coordinates not entered correctly
Explain the difference between a geographical projection system and a projected coordinate system. Provide examples for both.
Explanation / Answer
Answer
1. The answer is d) both a and b. The data query is of two types, Spatial (query by location) and Attribute (query by attribute). Spatial query refers to retrieving a data subset from a map layer by working directly with map features. Although both raster and vector data use Boolean connectors, raster data query uses these connectors to isolate raster cell values from other cell values within one raster map and link the selected cell values to cell values of other raster layers, whereas, It can be applied to a single vector file as they can store multiple attributes simultaneously.
2. The answer is c) Graduated symbols. Graduated symbol maps are maps that use visual variable of size to represent differences in the magnitude of abruptly changing phenomenon. These maps, unlike unclassed proportional symbols, are classed ones. So, the given map uses graduated symbols.
3. The answer is d) coordiantes not entered correctly. If this happens, what is described in the given question, coordinates get changed each time we do the change and save data in the new projection. So, it is necessary to check the coordinates carefully.
Difference between a geographical projection system and a projected coordinate system:
Geographical projection system is defined by a three-dimensional spherical surface and measured in latitude and longitude, while, projected coordinate system is defined by a two-dimensional surface and can be measured in the units if meter and feet. Also, a projected coordinate system is based on a geographical projection system. In addition to geographical projection system, a projected coordinate system includes a map projection, a set of projection parameters that customize the map projection for a particular location, and a linear unit of measure.
Examples: Geographical projection system-WGS 1983
Projected coordinate system-USA Albers Equal Area Conic
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