Spatial Data - GIS and Mapping - Lecture Slides, Slides of Geochemistry

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GISGeographic Information Systems (GIS)andSpatial Data

What is a GIS?

At the most basic level, a GIS is acomputer system capable of storingand manipulating spatial data

What is a GIS?^ „^ Mapping is a key output of GIS but is notthe whole story.^ „

GIS stores the spatial data that is used tomake maps. „ GIS is an analysis tool

A GIS is a tool to answerspatial questions …^ „^ Where is a site where certain conditions aresatisfied?^ „^ What changes have occurred since the lasttime data was collected?^ „

How will the runoff rate for a basin change if theland use changes?

„^ What spatial patterns exist in your data?

Questions the user needs toask: „^ Using a GIS, a suggested process for^ users:^ „^

What questions do you want answers for? „ What data do you need to find the answers? „ How do you process your data to find the answers to your questions?

How does a GIS work?

„^ Data acquisition^ „

Field collection with GPS „ Scan maps „ Digitize Maps

„^ Data integration^ „

Projection and registration „ Data structures or data types^ (raster vs vector)

„^ Mapping and analysis tools

Spatial Analysis „^ Compare different layers of spatial data „^ Combine elements of diverse data

Points in Polygon^ Which land use is well #1 sited in?

Vectorprocessing

Buffers

What are the characteristicsa stream?

Vector processing of land within 50 meters of

Visibility

What land is visiblefrom the selectedlocation? Raster processing

Data in a GIS …

What is spatial data? „^ Any data that is associated with a specificgeographic location^ „^

Aerial photography „ Remotely sensed imagery „ Road networks „ Wetlands delineation „ Stream gauges „ Dam sites

Spatial Data Types^ „^

Raster^ „^ Remotely Sensed Imagery (with datafor individual bands), DEMs „ Vector^ „^ Points^ „^ Lines^ „^ Polygons „ Image^ „^ (scanned images, georeferenced)

Raster data^ „^ Matrix of numbers (or cells)^ „^ Represents the entire area, whether anyof the map phenomena exists or not^ „^ Best representation for phenomena thatvaries continuously over the surface ofthe earth (rainfall, elevation)