GEOGRAPHIC INFORMATION SYSTEMS Lecture 15: Data Sources GIS Data Sources - understanding where to go to obtain data is an essential component of becoming a proficient GIS user - there is a tremendous amount of GIS data available for download, but it is scattered all over the Internet - basemap data - basemap data are layers that you might normally use in any project 1) administrative boundaries (e.g. county, state polygons) 2) populated places (cities, towns) 3) transportation (roads and railroads) 4) hydrography (rivers and lakes) 5) elevation (digital elevation model) 6) imagery (digital airborne or satellite) - other layers - other data layers tend to be topic specific (and form the main theme of your map) physical environment: landuse, soils, climate, geology, vegetation human environment: demographic, economic, agricultural, cadastral Options for Adding GIS Data - when you are working with ArcMap, there are several options for adding data to your map - add a basemap - add a basemap as a map service from Esri directly from ArcMap - must have an Internet connection - map services have very nice scale-dependent viewing (detail increases as you zoom in) - can work well as a basemap layer (but annotation is often chopped off on the map edge) - disadvantage: can’t save, manipulate, analyze or edit the data - add data from ArcGIS Online - sometimes ArcGIS Online is difficult to search - but there are a lot of data layers available - can add individual layer package from ArcGIS Online or a map service (of a topic-specific layer) - most data layers come in the form of a layer package (.lyr) - a layer package includes the data and the symbology to go with it - add the layer package to ArcMap - then export the data to your drive - add data from primary sources - examples of US primary data sources include… - USGS National Map Viewer - NRCS Geospatial Data Gateway - US Census Bureau - examples of Texas primary data sources include… - TNRIS - General Land Office (GLO) - add data from other sources - if you still can’t find the data you want - try a Google search - which tends to work quite well Obtaining Basemap Data – Importance of Scale and Data Sources - keep in mind that there is a scale associated with every data layer - some data layers are quite detailed and others are quite generalized - for example: TIGER data from the Census Bureau were digitized from 1:100,000 scale maps StratMap data for Texas were digitized from 1:24,000 scale maps (StratMap stands for the Texas Strategic Mapping Program) 1) administrative boundaries (national, state, county and city boundaries) - some administrative boundary layers are detailed and some are more generalized - thus, the best administrative boundary layer depends on the scale of the map - use data from ArcGIS Online or StratMap data from TNRIS

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2) populated places - depending upon the scale of your project, you might need data as points or polygons - ArcGIS Online is a good source for both 3) transportation - roads and streets - be aware that most road and street layers are often out-of-date - the most up-to-date layers are created by private companies and are not in the public domain - for Texas, the best road layer is the StratMap transportation layer available from TNRIS - or use the road data from ArcGIS Online - railroads - most railroad companies maintain their own data - but do not share it in the public domain - these layers are often out-of-date or inaccurate - it is often best not to use railroad data on a map if you can avoid it 4) hydrography (rivers and lakes) - in the TIGER data, rivers are line features and lakes are polygon features - these layers work well for cartography, but cannot be used for hydrologic analysis - the National Hydrography Dataset (NHD) is a modified version of the TIGER data - the lines that represent rivers are connected through lakes to allow for hydrologic modeling - use data from ArcGIS Online, StratMap, or direct from National Hydrography Dataset (NHD) 5) elevation (digital elevation models are called DEMs) - DEMs can be obtained at several different resolutions (grid cell size) - whereas a 30m grid cell is appropriate for county level analysis, a 1 km DEM is more appropriate for maps at the national, continental or global scale - download 30m DEMs from the USGS National Map Viewer 6) imagery - the best high-resolution imagery for the entire nation is NAIP imagery - NAIP stands for the National Agricultural Imagery Program - the imagery is collected as part of a joint effort by the USDA, USGS and the states - higher resolution data might be available for individual cities - the City of Lubbock and the Texas Tech both have very high-resolution (6 inch) imagery - normally, we will use NAIP imagery from NRCS Gateway Common Acronyms - many of the GIS data layers are referred to using a set of common acronyms - and it is important that professionals be familiar with these acronyms and the datasets they represent. DEM – Digital Elevation Model - raster elevation grids used in the analysis of topography - can be used to create contour maps, slope maps, aspect maps, hillshades - widely used in hydrology to define watersheds boundaries and stream networks - download 10m or 30m DEMs from the USGS National Map Viewer DRG – Digital Raster Graphics - scanned digital image of a topographic map - images are georeferenced and re-projected to UTM coordinates - a “collared” DRG includes the marginalia around the map body on a topographic map - an “uncollared” DRG has no marginalia – but it can be used to create a mosaic (of connected DRGs) - mostly 1:24000, 1:100000, and 1:250000 scale topographic maps - can be used as a source layer for digitizing features – but most DRGs are out of date - for Texas, download DRGs from TNRIS - available as individual 1:24K, 1:100K, 1:250K maps - or as a 1:24K county mosaic - for other states, download from USGS National Map Viewer

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DLG – Digital Line Graph - scanned separate (layers) from a 7.5’ topographic map - scanned separate (raster image) is then vectorized to create vector lines - the DLG - usually refers to elevation contour lines - can also be hydrography, roads or other layers - download contours (called hypsography) from TNRIS DOQ – Digital Orthophoto Quad - high-resolution georeferenced and orthorectified digital imagery for the U.S. - digital image covers one 7.5' topographic map - georeferenced means that the image is tied to real-world coordinates - images are georeferenced and projected to UTM coordinates - orthorectified means that the image is adjusted to account for terrain-induced changes in scale - normally 1 to 2 m resolution (pixel size) - can be color infrared (CIR) or natural color (NC) - can be used as a map background or as a source layer for digitizing features - download from TNRIS as DOQQs or compressed county mosaics (see below) Orthorectification – is a process to stretch an image to account for terrain-induced changes in scale. Image scale is determined by the focal length of the camera (which stays constant) and the height of the camera above the ground. When the ground is closer the image scale is larger and vice versa. Orthorectification adjusts the image for changes in ground height. DOQQ – Digital Orthophoto Quarter Quad - high-resolution georeferenced and orthorectified digital imagery covering the U.S. - digital image covers one quarter of a 7.5' topographic map - other attributes are the same as a DOQ - can be used as a map background or as a source layer for digitizing features - download DOQQs from TNRIS NAIP Imagery – National Agriculture Imagery Program - high-resolution georeferenced and orthorectified digital imagery for the U.S. - imagery is derived from digital airborne photography - commonly distributed as a county mosaic - image covers one county - normally 1 to 2 m resolution (pixel size) - can be color infrared (CIR), natural color (NC) or both - can be used as a map background or as a source layer for digitizing features - download NAIP county mosaics from NRCS Geospatial Gateway or NAIP DOQQs from TNRIS

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GIST 3300 / 5300 Geographic Information Systems GIS Data Sources Data Sources - add a map service from Esri - add data from ArcGIS Online

- find data using a Google search - admin boundaries, pop places, transportation, hydrography, elevation, imagery

- common acronyms: DEM, DRG, DLG, DOQs, DOQQs, and NAIP

Geographic Information Systems

Data Sources To create a map (or do any kind of analysis) – we need digital data! - this is one of the biggest problems with geographic information systems

- data is scattered all over the Internet - so what do you do?

Geographic Information Systems

Data Sources Basemap data layers

1) administrative boundaries (polygons) 2) populated places (cities, towns) 3) transportation (roads, railroads)

4) hydrography (rivers and lakes) 5) elevation (digital elevation model) 6) imagery (digital airborne or satellite)

Other layers - physical environment (landuse, soils, climate, geology, vegetation, etc)

- human environment (demographics, economic, agricultural, cadastral, etc)

Geographic Information Systems

Data Sources Add a basemap Add a complete basemap as a map service from Esri directly into ArcMap

- must have an Internet connection - very nice scale dependent viewing -often works great as a background layer (but annotation often gets chopped off)

- can’t edit, manipulate, analyze or save the data on these basemaps Geographic Information Systems

Data Sources Add data from ArcGIS Online Can be a map service or preferably a layer package from ArcGIS Online

- a lot of data - often difficult to search - most data comes in the form of a layer package (.lyr)

- layer packages contain actual data you can edit, symbolize, classify, analyze or save Geographic Information Systems

Data Sources Add data from primary sources US Data Sources USGS National Map Viewer NRCS Geospatial Data Gateway US Census Bureau Texas Data Sources TNRIS General Land Office

Geographic Information Systems

Data Sources Add data from other sources Google it!

Geographic Information Systems

Data Sources Importance of Scale and Data Sources TIGER data – U.S. Census Bureau digitized 1:100,000 topographic maps administrative boundaries, rivers and roads StratMap data – TNRIS – mostly derived from USGS 1:24,000 topographic maps StratMap stands for the Texas Strategic Mapping Program

administrative boundaries, rivers and roads and more at a more detailed scale

Geographic Information Systems

Data Sources Basemap data - administrative boundaries (ArcGIS Online, Texas StratMap) - populated places (ArcGIS Online)

- transportation (ArcGIS Online, Texas StratMap, private companies) - hydrography (ArcGIS Online, TIGER, StratMap, National Hydrography Dataset)

- elevation (hypsography) (USGS National Map Viewer) - imagery (NRCS NAIP imagery, local sources)

- or you can use the data in the Esri_Data folder in the lab

Geographic Information Systems

Data Sources Common Data Acronyms

When you are searching for data you also need to be familiar with a few common acronyms use to describe GIS data layers.

- DEMs - DRGs

- DLGs - DOQs - DOQQs and

- NAIP Imagery

Geographic Information Systems

Data Sources DEM – Digital Elevation Model - raster elevation grid used in the analysis of topography - can be used to create contour maps, hillshades, slope and aspect maps - widely used in hydrology to define watersheds boundaries and stream networks

- download from USGS National Map Viewer

Geographic Information Systems

DEMs, DRGs, DLGs and Imagery

DRG – Digital Raster Graphic

- scanned digital image of a topographic map - images are georeferenced and re-projected to UTM coordinates - “collared” DRGs include the marginalia around the map body of a topographic map

- ”uncollared” DRGs have no marginalia - can be used to create a mosaic (of connected DRGs) - DRGs are mostly scanned 1:24,000, 1:100,000 and 1:250,000 topographic maps - can be used for digitizing features - but most DRGs are out of date - download from TNRIS or USGS National Map Viewer

Geographic Information Systems

DEMs, DRGs, DLGs and Imagery

DLG – Digital Line Graph - scanned separates (plastic layers) used to create a 7.5’ topographic map - usually refers to elevation contours - can also be rivers, roads or other layers - scanned separate (e.g. contours) is then vectorized to produce a vector layer

- some downloads available from TNRIS

Geographic Information Systems

DEMs, DRGs, DLGs and Imagery

Imagery: DOQ – Digital Orthophoto Quads - georeferenced air photo image - cover one 7.5’ topographic map - normally 1m to 2 m image resolution (pixel size) - 1980s - originally developed as a paper map product - mostly black/white (grayscale) imagery Imagery: DOQQ – Digital Orthophoto Quarter Quads

- 1990s - became available as downloadable 3.75’ quarter quads (DOQQs) - can be either natural color (NC) or color infrared (CIR)

Geographic Information Systems

DEMs, DRGs, DLGs and Imagery

Imagery: Orthorectification - DOQs and DOQQs are orthorectified - orthorectification – a process used to stretch an image to account for terrain induced changes in scale (not as important for flat areas like Lubbock).

Image scale is determined by the focal length of the camera (constant) and height of camera above the ground

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Height of ground changes beneath the flight path

When the ground is closer the scale is larger, when the ground is farther away, the scale is smaller. Geographic Information Systems

DEMs, DRGs, DLGs and Imagery

Imagery: NAIP - National Agriculture Imagery Program (2000s)

- digital aerial imagery covering the US – not satellite! - orthorectified to account for terrain induced changes in scale - georeferenced and projected to UTM coordinates - normally 1 to 2 m resolution - can be used as a basemap for digitizing

- can be natural color or color infrared

Geographic Information Systems

DEMs, DRGs, DLGs and Imagery

Imagery: NAIP - National Agriculture Imagery Program (2000s) - 2000s – NAIP became available as downloadable county mosaics - can be either natural color (NC) or color infrared (CIR) - 2010s - integrated into the new generation of digital topographic maps (PDFs) - maps use natural color (NC) imagery

- download from NRCS Geospatial Gateway or TNRIS

Geographic Information Systems

Geographic Information Systems