Module 9 Flashcards
Define spatial analysis and provide two examples we have talked about in the past
▪ spatial analysis refers to a set of methods used to examine, summarize, manipulate, and predict spatial patterns, spatial relationships, trends, and their underlying causes ▪ spatial analysis provides a means of turning spatial data into useful information and knowledge, and is the central component for environmental problem solving and decision making ▪ the product of spatial analysis is composed of new datasets, and maps and tables demonstrating the results of the applied analysis
we’ve already seen some of these methods:
▪ attribute and location queries are relatively simple approaches to identifying
where certain phenomena exist or where one phenomena exists in relation to
another
▪ network analysis uses specifically designed network datasets to assess spatial
relationships and use least-cost approaches for answering various research
questions
there are 2 ways to select features in GIS
– interactive selection or query selection
Rules of SQL Queries(5)
▪ rules for evaluation:
1. expression always evaluated left to right
2. expressions within parentheses assume highest
priority
3. if parentheses are nested, the evaluation starts
with the innermost parentheses
4. AND is evaluated before OR
5. NOT is evaluated before AND and OR
Reclassification for vector and raster
▪ reclassification is used to recode the attributes of features in the attribute table or
reclassify the grid values to produce a new raster layer
Vector:
▪ with vector data, the field calculator is used to reclassify a field in the attribute table
▪ assign new values to classes or ranges of the existing
values to reduce the number of classes or ranges in the
original input layer
▪ group attribute values into categories in a new
classification scheme
-the primary goal of vector reclassification is to take many different feature types and group them into a lesser number of feature types
Raster:
raster reclassification is commonly used for DEMs, where the high resolution continuous surface is reclassed into discrete elevation bands, or to produce binary maps (presence / absence)
▪ assign ranks, orders, ratings, or weights representing preference, importance,
priority, sensitivity, suitability, capability, or other criteria to unique values,
ranges, or categories of values in the input layer
▪ eg, use reclass to assign new values to different land use classes based on
their ecological importance to help identify areas of high conservation value
▪ eg, use reclass to assign values 1 – 10 to different ranges of slope to represent
landslide risk
Vector Reclassification is a..
this is why it is a data
simplification technique
For a _______ coordinate system the shortest distance between two points is a straight line versus a _____ coordinate system which is a curved line(great circle)
projected
geographic
Raster area is calculated by
area is calculated as the cell resolution multiplied
by the number of cells in the polygon
3 CATEGOIRES OF SHAPE MEASURES
- Compactness:quantifies how far a feature deviates from a standard shape (a circle or square), which is considered to be the most compact
2.Boundary:quantitatively describe the roughness or the smoothness of a feature’s outer edge (a smoother boundary has fewer edges), and is an
indicator of shape complexity
3.Form: quantify the overall geometric configuration of a feature by comparing it to a standard shape such as a circle
for standard shapes SIc(compactness) = \_\_ and the further below that number...
1
means its less compact
-anything <1
for standard smoothness of the boundary is __ and as it gets rougher it is closer to __
1
2
buffering
▪ buffering is a common vector data distance measurement tool that creates a zone
around a feature or a set of features with a specific width – the zone is called a
buffer
Using dissolve when buffering mean..
that the objects, if they have overlapping buffers, will connect instead of each having individual overlaps
▪ in a projected coordinate system, the buffer distance
is measured in _______ as a ______ buffer
▪ in a geographic coordinate system, the buffer size is
determined by _____ distance measurement
cartesian space, Euclidean
geodesic
ringed buffers
.ringed buffers are common to use when the influence diminishes with distance from the feature
vector uses buffers while rasters use..
distance surfaces