GIS Data Formats, Coordinate Systems, and Map Projections

Aprx

project file

- stores everything related to the project

Ppkx

packaged project

Bookmarks function

return to a specific viewpoint on your map

Save project as

Renaming the project

TIFF

tagged image file format

- high-quality images

- uncompressed, larger sizes

GIF

Graphic interchange format

- small file

- ideal for simplistic drawings

JPEG

Joint photographic experts group

- most widely used for photographs

Feature attribute table

every feature has a record with attribute tables

Data (non-spatial) tables

Tables you can add

- Can add lat & long info but has to be processed to be seen

- can join to feature class to add more attributes

XY Data

Point data table with X and Y attributes (such as lat and long)

- you can do this in a standalone table and display xy data and it is a tool in geoprocessing

Exporting a feature class

you can go to copy feature geoprocessing select from outside the input and name the output whatever you want

Plain ASCII text with comma separated values (.csv)

- Very transportable format, very large files

- Each table record is row terminated with a line-break character (invisible, nonprinting value)

- Has values often separated by comma

Excel

.xls, .xlsx over a million rows and thousands columns allowed

dBase database table

.dbf Field names can only be 10 characters long and has max of columns

microsoft access database

.mdb

Geocodes

used to join external tables

FIPS Codes (2000)

- Federal information processing standards

- Codes for place names throughout the world

ANSI Codes (2010)

- Replaces FIPS codes

- does counties, cities, places

How to determine ANSI codes

first two #s will be the state then next 3 are the county and last #s are the minor civil division

ANSI statistical boundaries

- depending on the boundary how many digits after state and county

Tract: 6 digits

Block group: 7 digits

Block: 10 digits

ESRI Legacy Format

- Folder that has multiple files

- Can have points, lines, and/or polygons

- Has several intermediate data products like topology to speed up processing

- Multiple files, all having the same name but different file extensions

Geodatabase

container used to hold a collection of datasets

Personal Geodatabase

Stores datasets in a Microsoft access

- when you add data you go to the database to choose features, tables, or rasters

Difference between geodatabase and a project file

Geodatabase stores and organizes feature classes, tables, rasters. It can be used across multiple projects. A project file is your workspace for creating maps, layouts, data references and is specific to the project you are working on

Map Scales (1:24,000)

1 in on the map is 24,000 in. on the ground

Latitude

(parallels) 0 latitude (equator) 90° north and south

Longitude

(meridians) 0 longitude (vertical in the center) 180° east and west

Decimal Degrees

ex. 40° 26' 2'' 40+26/60 + 2/3600 = 40.43385°

- if it is west or south make sure it is negative!!!

Cartesian Coordinate System

X, Y coordinates, feet or meters

State Plane Coordinates

- Most US local governments use this type of data

- All positive coordinates in feet or meters

- There is 125 zones. And at least one for each state

UTM (Universal Transverse Mercator)

- Used by US military and federal organizations

- Covers world besides north pole and south pole since no one really lives there

Have a specific zone

Metric coordinates

Map Projections

way to represent the curved surface of the earth on the flat surface of a map

Types of projections

- Planar (looks like a rectangle)

- Cylindrical (cylinder)

- Conic (triangle)

Conformal Projection

cylindrical, tangent to the equator

Direction is preserved, which is the good part but large objects can be distorted

Equivalent Projection

- Probably used most often

- It is a conic projection and preserves accurate area

- Shape and scale are not preserved but minimal distortion between standard parallels

- Good for finding distance, area

Compromise Projections

Looks proportional, looks better than the other projections, but doesn't preserve properties (why it is called compromise projections)

When projection is important vs not important

Important: small-scale maps

Not important: large-scale, business, policy

Coordinate systems

either through options or contents, projections/properties, coordinate system