1. You want to know what GIS is.
2. You know what GIS is, but want to know more about GIS.
2. You know what GIS is, but want to know more about GIS.
What's on This Page:
GIS Definition:
Rather than repeat the many varied definitions of GIS, here's an excellent definition of GIS
(thanks to Wikipedia) with some examples:
http://en.wikipedia.org/wiki/Geographic_information_system
Here's a definition from the ESRI website (http://www.esri.com/what-is-gis/index.html):
Wow! That is quite a lot! However, you don't have to understand all that; just need to know what you can do with the data and how you can use it. Remember, you don't have to understand how a car works; you just get in and drive it!
So now that you (hopefully) have a basic understanding of what GIS is, what types of data is considered "GIS data"?
Here's a definition from the ESRI website (http://www.esri.com/what-is-gis/index.html):
A geographic information system (GIS) integrates hardware, software, and data for capturing,
managing, analyzing, and displaying all forms of geographically referenced information.
GIS allows us to view, understand, question, interpret, and visualize data in many ways that reveal relationships, patterns, and trends in the form of maps, globes, reports, and charts.
A GIS helps you answer questions and solve problems by looking at your data in a way that is quickly understood and easily shared.
GIS allows us to view, understand, question, interpret, and visualize data in many ways that reveal relationships, patterns, and trends in the form of maps, globes, reports, and charts.
A GIS helps you answer questions and solve problems by looking at your data in a way that is quickly understood and easily shared.
Wow! That is quite a lot! However, you don't have to understand all that; just need to know what you can do with the data and how you can use it. Remember, you don't have to understand how a car works; you just get in and drive it!
So now that you (hopefully) have a basic understanding of what GIS is, what types of data is considered "GIS data"?
GIS Data:
There are two types of GIS data: Raster data and vector data.
Raster Data is data contained in grids (imagery).
The easiest way to remember what raster data is to remember that an image is actually a grid, i.e.,
pixels in rows and columns that when assembled correctly gives you an image! Raster data is contained
in imagery such as:
Vector Data is data contained in lines or polylines, points,
and polygons (areas):
USGS Digital Elevation Model (DEM):
USGS Digital Line Graph (DLG):
USGS Digital Orthoimagery Quarter Quad (DOQQ):
USGS Digital Raster Graphic Enhanced (DRGE):
There are many other types of raster data; I've just listed the more common types!
Not sure what a Digital Elevation Model is? The following web pages explain what DEMs are:
USGS Digital Line Graph (DLG):
Not sure what a Digital Line Graph is? The following web pages explain what DLGs are:
When available, DLGs consist of several layers for each 1:24,000 scale map (vector) data USGS defined quad:
USGS:
http://eros.usgs.gov/#/Guides/dlg
- Warning: This web page is quite technical!
Wikipedia: http://en.wikipedia.org/wiki/Digital_line_graph
Wikipedia: http://en.wikipedia.org/wiki/Digital_line_graph
When available, DLGs consist of several layers for each 1:24,000 scale map (vector) data USGS defined quad:
Boundaries (DLG code BD): Includes state, county, city, and other national and State lands such as
forests and parks
Hydrography (DLG code HY): Includes flowing water, standing water, and wetlands
Hypsography (DLG code HP): Includes contours and supplementary spot elevations
Manmade features (DLG code MS): Includes cultural features not collected in other data categories such as buildings
Nonvegetative features (DLG code NV): Includes lava, sand, and gravel
Pipelines, Transmission Lines, and Miscellaneous Transportation Features (DLG code MT)
Public Land Survey System (DLG code PL): Includes township, range, and section line information
Railroads (DLG code RR)
Roads and trails (DLG code RD)
Survey control and markers (DLG code SM): Includes horizontal and vertical positions (third order or better)
Transportation: See roads and trails (DLG code RD), railroads (DLG code RR), pipelines (DLG code MT), and transmission lines (DLG code MT)
Vegetative surface cover (DLG code SC): Includes woods, scrub, orchards, vineyards, and vegetative features associated with wetlands
Hydrography (DLG code HY): Includes flowing water, standing water, and wetlands
Hypsography (DLG code HP): Includes contours and supplementary spot elevations
Manmade features (DLG code MS): Includes cultural features not collected in other data categories such as buildings
Nonvegetative features (DLG code NV): Includes lava, sand, and gravel
Pipelines, Transmission Lines, and Miscellaneous Transportation Features (DLG code MT)
Public Land Survey System (DLG code PL): Includes township, range, and section line information
Railroads (DLG code RR)
Roads and trails (DLG code RD)
Survey control and markers (DLG code SM): Includes horizontal and vertical positions (third order or better)
Transportation: See roads and trails (DLG code RD), railroads (DLG code RR), pipelines (DLG code MT), and transmission lines (DLG code MT)
Vegetative surface cover (DLG code SC): Includes woods, scrub, orchards, vineyards, and vegetative features associated with wetlands
USGS Digital Orthoimagery Quarter Quad (DOQQ):
Not sure what a Digital Orthoimagery Quarter Quad is? The following web pages explain what DOQQs are:
NOTE: These are also known as Digital Orthophoto Quarter Quadrangles (DOQQs).
USGS Digital Raster Graphic Enhanced (DRGE):
Not sure what a Digital Raster Graphic Enhanced is? The following web pages explain what DRGEs are:
It should be noted there are two types of DRGEs:
NOTE: DRGEs are also known as topoquads or topographic (quadrangle) maps!
It should be noted there are two types of DRGEs:
Collard DRGEs are scanned images of a USGS standard series topographic map, including all map
collar information (the text you see around the edges of a printed map). These are NOT suitable
for most GIS software programs!
Non-collared (sometimes referred to as "seamless"): These are similar to the collared DRGE except they contain NO collar information. They are suitable for use in most GIS software programs! They normally are available in a compressed file format because they MAY contain more than one file:
Non-collared (sometimes referred to as "seamless"): These are similar to the collared DRGE except they contain NO collar information. They are suitable for use in most GIS software programs! They normally are available in a compressed file format because they MAY contain more than one file:
1) .TIF - Geotif image of a map, readable by lots of software. Some software will recognize the
map projection and coordinates. Other software will complain that it cannot read a TIFF tag,
but will otherwise read the image.
2) .TFW - File describing the transformation from row/column to UTM NAD27 coordinates.
3) .FGD - Metadata file
Some downloads may contain additional files.
2) .TFW - File describing the transformation from row/column to UTM NAD27 coordinates.
3) .FGD - Metadata file
Some downloads may contain additional files.
NOTE: DRGEs are also known as topoquads or topographic (quadrangle) maps!
There are many other types of raster data; I've just listed the more common types!
Vector data comes in a variety of formats. If you are looking for GIS software, try to find a program
that can use as many formats as possible. There are some good free GIS programs out there, but you will
probably end up having to pay to get a good GIS program. You might want to look at your data to see
what format(s) it's in and then look for a GIS program that can use those formats.
So what type of formats can vector data come in. I've seen it in many of the following formats:
The number of vector data formats is a varied as the data itself!
So what type of formats can vector data come in. I've seen it in many of the following formats:
DEM (USGS)
E00 (ESRI ArcInfo file)
DXF (AutoCAD DXF)
SHP, SHX, and DBF (ESRI shapefiles)
SDTS (USGS)
TIGER (normally from the US Census Bureau)
E00 (ESRI ArcInfo file)
DXF (AutoCAD DXF)
SHP, SHX, and DBF (ESRI shapefiles)
SDTS (USGS)
TIGER (normally from the US Census Bureau)
The number of vector data formats is a varied as the data itself!
Datums and Projections:
OK, so now you've got all this data and want to display it. How do you accomplish that?
There are two things you must know about your data:
I can hear you now: "What is the what and what?" and why do I need to know that datum and projection of my data?
Let me break it down into the two parts:
Datums:
Projections:
There are two things you must know about your data:
1. What is the datum of the data?
2. What is the projection of the data?
2. What is the projection of the data?
I can hear you now: "What is the what and what?" and why do I need to know that datum and projection of my data?
Let me break it down into the two parts:
Datums:
A datum is a reference point. if you've ever seen a USGS topographic map, it has a datum.
See the horizontal and vertical lines on the map. Those are reference lines for the map's datum.
And if you check in the lower left corner of the map, you'll see a reference to the map's datum:
<------ Map datum and projection
The line that reads "zone 11, shown in blue. 1927 North American Datum" is the map's datum (and projection).
Problem is, there are hundreds of datums! The ones you are likely to need (in the USA) are:
Now that you've got the datum understood, you have to deal with the projection!
And if you check in the lower left corner of the map, you'll see a reference to the map's datum:
<------ Map datum and projection
The line that reads "zone 11, shown in blue. 1927 North American Datum" is the map's datum (and projection).
Problem is, there are hundreds of datums! The ones you are likely to need (in the USA) are:
NAD 27 : North American Datum 1927; used by older USGS topographic maps and Canadian maps
NAD 83 : North American Datum 1983; used by newer USGS topographic maps in the future
WGS 84: World Geodetic System 1984; a datum for the whole world as used by most GPS; DEFAULT "out of the box" datum for most GPS units
NAD 83 : North American Datum 1983; used by newer USGS topographic maps in the future
WGS 84: World Geodetic System 1984; a datum for the whole world as used by most GPS; DEFAULT "out of the box" datum for most GPS units
Now that you've got the datum understood, you have to deal with the projection!
Projections:
GIS data uses projections to display the map in your GIS software.
Projections are basically grids that help you pinpoint exact locations on your data/maps.
Again, as with datums, there are hundreds of projections! The ones you are likely to need (in the USA) are:
As I mentioned above, one of the problems you will come across, sooner or later, is trying to get all your data into one datum and projection.
Fortunately most of today's GIS software allows you to "reproject" data. This works by selecting the default/base datum and projection and then as you add the various GIS data, the program will automatically adjust (" reproject") the data to fit your default/base datum and projection!
Projections are basically grids that help you pinpoint exact locations on your data/maps.
Again, as with datums, there are hundreds of projections! The ones you are likely to need (in the USA) are:
UTM : Universal Transverse Mercator
Lat/Long : Latitude/longitude
Special note about UTM: The UTM projection system consists of "zones". You may have trouble when you attempt to project data over two different UTM zones! Some GIS software does this well; other GIS software will leave a blank between the UTM zones! Beware!
Here's a link to a PDF that shows the UTM zones for the US:
Lat/Long : Latitude/longitude
Special note about UTM: The UTM projection system consists of "zones". You may have trouble when you attempt to project data over two different UTM zones! Some GIS software does this well; other GIS software will leave a blank between the UTM zones! Beware!
Here's a link to a PDF that shows the UTM zones for the US:
As I mentioned above, one of the problems you will come across, sooner or later, is trying to get all your data into one datum and projection.
Fortunately most of today's GIS software allows you to "reproject" data. This works by selecting the default/base datum and projection and then as you add the various GIS data, the program will automatically adjust (" reproject") the data to fit your default/base datum and projection!
GIS Software
Probably one of the most well-known GIS programs is ArcGIS from
ESRI. ArcGIS is actually a suite
of GIS software consisting of many programs. While this is very good software, it is very expensive. And it
has a very steep learning curve!
Another program that can do many of the things ArcGIS can do is GlobalMapper. It is available here: www.globalmapper.com. There is a demo that can be downloaded so you can work with the software to determine if it will meet your needs.
A free program is Quantum GIS that is available here: http://www.qgis.org/. I used to use this software - mainly because of it's price. However, after several updates that were not backward compatible (meaning you'd have to completely re-import all your data), I decided to forgo this software and pay for GlobalMapper!
Here's a web page (thanks to Wikipedia) that lists many GIS software programs: http://en.wikipedia.org/wiki/List_of_geographic_information_systems_software. If you scroll down to the "See Also" section, you can click on a link that displays a table of GIS software and shows which operating systems the software runs on.
Another program that can do many of the things ArcGIS can do is GlobalMapper. It is available here: www.globalmapper.com. There is a demo that can be downloaded so you can work with the software to determine if it will meet your needs.
A free program is Quantum GIS that is available here: http://www.qgis.org/. I used to use this software - mainly because of it's price. However, after several updates that were not backward compatible (meaning you'd have to completely re-import all your data), I decided to forgo this software and pay for GlobalMapper!
Here's a web page (thanks to Wikipedia) that lists many GIS software programs: http://en.wikipedia.org/wiki/List_of_geographic_information_systems_software. If you scroll down to the "See Also" section, you can click on a link that displays a table of GIS software and shows which operating systems the software runs on.
Where to Download GIS Data From
Everyone is putting their GIS data online! But you have to know where to find it. There is no central web
site showing all the GIS data available online. Government GIS data is available at the federal, state,
county, and city/town level. But finding it can be a challenge!
If you do a search for "GIS data" (the quotes are important!) and the location you want the data from, such as federal government agency name, state name, county name, or city/town name, you should find the GIS data.
Due to several projects I am currently involved with, I have located GIS data sources for Washington, Idaho, Montana, and Oregon, and listed them below:
If you have questions about anything contained on this web page, please feel free to e-mail me using the following link:
If you do a search for "GIS data" (the quotes are important!) and the location you want the data from, such as federal government agency name, state name, county name, or city/town name, you should find the GIS data.
Due to several projects I am currently involved with, I have located GIS data sources for Washington, Idaho, Montana, and Oregon, and listed them below:
IDAHO:
MONTANA:
OREGON:
WASHINGTON:
DEM:
http://data.geocomm.com/catalog/US/61053/sublist.html
You must have to an account in order to download this data (accounts for downloading DEM data are free!).
You must know the USGS quadrangle name and the county the quadrangle is located in.
DLG:
You must have to an account in order to download this data (accounts for downloading DEM data are free!).
You must know the USGS quadrangle name and the county the quadrangle is located in.
http://edc2.usgs.gov/geodata/dlg_large/states/ID.php
You must know the USGS quadrangle name in order to download the appropriate DLG.
DOQ/DOQQ:
You must know the USGS quadrangle name in order to download the appropriate DLG.
http://insideidaho.org/geodata/USGS/DOQ.htm
This is a zoomable map. However, if you know the USGS quadrangle name, you can type it in and go directly to the download.
DRGE:
This is a zoomable map. However, if you know the USGS quadrangle name, you can type it in and go directly to the download.
? ? ?
MONTANA:
DEM:
http://data.geocomm.com/catalog/US/61047/sublist.html
You must have to an account in order to download this data (accounts for downloading DEM data are free!).
You must know the USGS quadrangle name and the county the quadrangle is located in to download the appropriate DEM.
DLG:
You must have to an account in order to download this data (accounts for downloading DEM data are free!).
You must know the USGS quadrangle name and the county the quadrangle is located in to download the appropriate DEM.
http://edc2.usgs.gov/geodata/dlg_large/states/MT.php
You must know the USGS quadrangle name in order to download the appropriate DLG.
DOQ/DOQQ:
You must know the USGS quadrangle name in order to download the appropriate DLG.
http://nris.mt.gov/nsdi/doq.asp
You must know the USGS quadrangle name in order to download the appropriate DOQ.
DRGE:
You must know the USGS quadrangle name in order to download the appropriate DOQ.
? ? ?
OREGON:
DEM:
http://data.geocomm.com/catalog/US/61056/sublist.html
You must have to an account in order to download this data (accounts for downloading DEM data are free!).
You must know the USGS quadrangle name and the county the quadrangle is located in to download the appropriate DEM.
DLG:
You must have to an account in order to download this data (accounts for downloading DEM data are free!).
You must know the USGS quadrangle name and the county the quadrangle is located in to download the appropriate DEM.
http://edc2.usgs.gov/geodata/dlg_large/states/OR.php
You must know the USGS quadrangle name in order to download the appropriate DLG.
DOQ/DOQQ:
You must know the USGS quadrangle name in order to download the appropriate DLG.
ftp://159.121.106.159/imagery/DOQ_NAPP_2/
You must know the DSN of the DOQ you wish to download. If you do not know the DSN, click the following link to learn about DSN:
DRGE:
You must know the DSN of the DOQ you wish to download. If you do not know the DSN, click the following link to learn about DSN:
? ? ?
WASHINGTON:
DEM:
See "ALL EXCEPT DLGs" below
Or you can download from this website: http://data.geocomm.com/catalog/US/61046/sublist.html
You must have to an account in order to download this data (accounts for downloading DEM data are free!).
You must know the USGS quadrangle name and the county the quadrangle is located in to download the appropriate DEM.
DLG:
Or you can download from this website: http://data.geocomm.com/catalog/US/61046/sublist.html
You must have to an account in order to download this data (accounts for downloading DEM data are free!).
You must know the USGS quadrangle name and the county the quadrangle is located in to download the appropriate DEM.
http://edc2.usgs.gov/geodata/dlg_large/states/WA.php
You must know the USGS quadrangle name in order to download the appropriate DLG
DOQ/DOQQ:
You must know the USGS quadrangle name in order to download the appropriate DLG
See "ALL EXCEPT DLGs" below
DRGE:
http://rocky2.ess.washington.edu/data/raster/drgclip/index.html
- clipped DRGEs
ALL EXCEPT DLGs:
NOTE: For Washington GIS data, you should select the following link which contains the GIS data
(DEMs, DOQs, and DRGEs [both collared and non-collared] by USGS 1° x 2° topoquad:
If you have questions about anything contained on this web page, please feel free to e-mail me using the following link:
