Layers often included in GIS maps

 

 

 

 

Map of land cover in the Boulder Creek Watershed. (2001 Land Cover from USGS, National Land Cover Database Zone 33 Land Cover Layer)

Remote sensing data is very useful for visualization, mapping, analysis, modeling

Map of geology in the Boulder Creek Watershed (from Murphy, 2006)

GIS (Geographic Information System) is a system of hardware and software used for storage, retrieval, mapping and analysis of spatial data.  GIS maps are made of layers, or collection of geographic objects that are similar.  For example, a layer could hold contain cities or streams.  To make a GIS map, one could add as many layers as needed.  A GIS layer may contain features or surfaces.  Features are geographic objects that can be represented by a polygon, line or point.   Examples of feature objects are rivers or countries.  Some data such as wind speed, temperature, rainfall and ocean depth have no distinct shape.  They are measurable values on the earth.  Such data are represented by raster, which is a matrix of identically sized square cells.  Each cell represents a unit of surface area and contains a measured value for that surface area.  A layer composed of raster make up a surface layer. 

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Remote sensing (RS) is a way to gather information about Earth from a distance by using special instruments mounted on airplanes, satellites or even ships.  On the surface of the earth, RS instruments measure the radiation reflected and emitted from the Earth at different wavelengths.  Under water, RS can map the ocean floor without traveling to the bottom of the ocean using reflected sound waves instead of light waves.  Light Detection and Ranging (LIDAR) is a type of remote sensing system used to collect topographic data.  LIDAR data are collected with aircraft-mounted lasers capable of recording elevation measurements at a rate of 2000 – 5000 pulses per second.  LIDAR is then used to construct a digital elevation model (DEM) which can be applied as a layer in a GIS map.  RS imagery is one of the fastest-growing sources for raster GIS data. 

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At the Boulder Creek CZO, all samples collected have a latitude and longitude.  Based on these samples, we can create various layers such as stream discharge, snow survey points and soil samples. Maps, DEMs, attribute data, surface layers and images can be displayed simultaneously and dynamically linked. This can help scientists answer various questions regarding the Boulder Creek CZO, such as:
(1)What controls the spatial variation in a critical zone
(2)How does critical zone development vary across erosional and ecological regmines
(3)How does the distribution of critical zone development control the hydrologic response of the catchment to snow and rainfall.

 

Written by Chi Yang