best practices file naming conventions files should not be named with spaces or any other special...
TRANSCRIPT
Shawn L. Penman, PhD
GIS Tips, Tricks and Best Practices
DataBest Practices
Data Names are Everything File Naming Conventions
Files should not be named with spaces or any other special characters in its name. ▪ Multiple-band grid cannot have more than 9
characters in its filename, and a single-band raster dataset cannot have more than 13 characters.
▪ File geodatabase – file system limit▪ Feature class or table name – 160 characters▪ Field name - 64 characters
▪ Shapefile – file system limit▪ Field name – 8 characters
Geodatabase (10.1 +)
Rename and change the field’s types in the file geodatabase after the field has been created.
• Open the feature class properties in a file geodatabase, navigate to fields and you’ll find out that you can now rename them.
And if the table is empty, say when you’re working on creating a schema for an empty feature class, you can even change the type of the field (i.e. switch from FLOAT to DOUBLE). This means you can stop creating new
fields and using the Field Calculator to copy the values if all you need to do is just rename the field. Jump to the feature class properties dialog and rename it!
Copy/Moving GIS DataALWAYS USE ARCCATALOG
NEVER USE WINDOWS EXPLORER!!!
Data Movement
Data Organization
Plan on data acquisition and normalization to take 75% of the time on a project
Normalization can include: Clipping data to study area boundary Data model
▪ Vector Raster▪ Raster Vector
Projection▪ UTM… StatePlane…
File format▪ Shapefile Geodatabase▪ Coverage Geodatabase
Best PracticesDocumentation
Metadata
Data about Data! Metadata is crucial when using existing
data sources Federal standard (FGDC & ISO) It is located in different places and it
comes in different formats *.xml - XML *.txt, *.met – ASCII Text *.html, *.htm - Web
Metadata
Typical Metadata sections Identification Information
▪ Source Information▪ Date
Data Quality Information▪ Processing Steps (who did it? And What did they do?)▪ Date of Processing
Spatial Organization Information Spatial Reference Information
▪ Projection & Datum Entity and Attribute Information
▪ Definitions (what do those weird field names mean?) Distribution Information
▪ Can it be shared? Or is it for in house use only?
Why? Demonstrates professional integrity and data
credibility. Makes it shareable and publishable; very helpful for
team members and collaborators (federal, state, local, private) you share data with/to.
Provides ongoing history and archive of a data set. May make grant awards/opportunities more likely. Protects against loss of institutional data
knowledge.
Why Metadata?
Datasets Catalogued in Excel
Compliments of Rick Koehler at New Mexico Energy, Minerals, and Natural Resources
Data OrganizationVia folders, mix of file formats
Compliments of Gar Clarke at New Mexico Department of Information Technology
Data Folder Structure
Project Name Data Reports Mxds Maps Archive
Organization Standards
Standards Departmental Standards? Office Standards? Personal Standards?
Need to develop/maintain a strategy for organizing your data
What happens when a team member leaves for a new job?
Best PracticesProjections & Coordinate Systems
Why are coordinate systems important? Without a coordinate system (including a datum and projection) a
map is not a map but only a drawing. There are many different ones - each one is better for certain
purposes. Unfortunately, there is no single best system.
How does that influence a GIS project? The “best” systems depends on what you want to do and where
you are located. Data from different sources may be from different systems. Not knowing the system for data you are working with can create
major headaches! So, always make sure you know the system you are working with.
Why?
Why Datums are Important
Impact of incorrect assignment of datums
Bridge layer incorrectly assigned NAD 1927 (actually NAD 1983)Stream and road layer NAD 1927
A coordinate system that divides the 50 US states, Puerto Rico and the US Virgin Islands into more than 130 numbered zones
Developed in the 1930s to provide a common reference system to surveyors - to maintain accuracy, many states had to be divided in zones - the boundary of zones within states follow county boundaries
Units in feet or meters Each zone has its own projection, which may be cylindrical or conic:
Lambert conformal conic for zones that are longer east-wets (e.g. Kentucky) Transverse Mercator for zones that are longer north-south (e.g. Illinois) Oblique Mercator for zones at an angle (e.g. Alaska panhandle)
To specify a location, you need to report: (X,Y) coordinate pair State Plane zone Datum Units
State Plane Coordinate System
State Plane Zones
State Plane Zones - NM
West
Central
East
3002
30013003
Projection & Coordinate System Jeopardy
Troubleshooting unknown coordinate systems In ArcCatalog, select a geographic dataset and with the Properties dialog
box examine the coordinate system and extent. If the coordinates have values between -180 and +180 in the x-direction and -90 and +90 in the y-direction you likely have geographic coordinates. The next step is to identify the datum used for the data. Globally, WGS84 is the current standard datum. In the US, NAD 1927 is common on old datasets and NAD 1983 is common for new US datasets.
If the data shows an extent in which coordinates to the left of the decimal are 6, 7or 8 digits, the data is probably in a projected zone. Try UTM first and identify the zone by looking at a national UTM zone map.
If UTM doesn’t work, then try whatever is the local coordinate system. For example in the US try the local State Plane Coordinate System zone. Then determine the datum.
If you observe offsets from a few meters to several hundred meters, then you are possibly seeing a datum shift. In the US NAD 83 datum is approximately 200 meters north of the same data reference to the NAD27 datum. Source: Modeling Our World, second edition. Zeiler
& Murphy
Projection Best Practice
Matching The coordinate systems of all the layers should match
each other and should match the coordinate system of the data frame.
If layers are being projected on the fly, there may be unexpected alignment problems when making edits.
ArcMap - A data frame maintains its own x, y tolerance, resolution, and domain values, which are taken from the first layer added to the map. Certain edits may fail, or features may collapse unexpectedly, because of the differences in these values between the data frame and the layers you are editing.
Best PracticesCartography & Data Presentation
Purpose of Map?
Figure for report Map for irate citizen Map published on website Public zoning presentation Large format map Will the map be viewed close up or at a
distance Will the map stand alone, or will it be
part of a series of maps that share a similar design
Map Objectives
http://kitkatpecson.com/portfolio/work/a-map-of-ice-and-fire/
Design Objectives Highlight Relationships Illustrate results
Share Information Fulfill Intended Purpose
Map Message
Floodplain boundaries New subdivision boundaries City council districts and floodplain
boundaries Redistricting of districts after census
Map Production Checklist
Timeline for map production
Purpose of map Format & size of map
printer? Data availability Create Draft
possibly multiple drafts
QA/QC Map Legibility Communication
Make Revisions Non-GIS person review Deliver Final Product
Paper Electronic
Presentation Report Poster Oral
Type of MapBest method of communication
Single Symbol Map
http://moroccoonthemove.com/wp-content/uploads/2014/05/Africas-Hottest-Investment-Zones-2014-1024x975.png
Unique Values Map
Graduated Color Map
Graduated Symbol Map
Dot Density Map
Chart Map
http://www.bom.gov.au/water/ssf/faq.shtml
Multivariate Map
https://andersolson.files.wordpress.com/2012/09/multivariatemap.jpg
Data DisplayBest Practices
How Many Classes?
3
7
5
9
Maximum = 7 most map readers can distinguish up to 7 different colors
on a color ramp or gray scale, so more than 7 classes will make it difficult to identify features in the same class
more than 7 classes can be used for continuous data (e.g. elevation, temperature)
Minimum = 3 fewer than 3 classes will not show much variation
Strategy first determine the proper classification scheme than start with large number of classes reduce number stepwise and select the minimum number
of classes which still shows the spatial pattern in sufficient detail
Deciding How Many Classes
The values of the class should be meaningful 73.857 % is too detailed 73.9 or 74 % is probably OK 70% may not be detailed enough
You can use standard classification schemes but typically it is better to force rounding to a certain number of digits.
For example: 17386.346 17386.34 17386.3 17386 17390 17400 17000 20000
Making Classes Easier to Read
Changing Symbol Properties
Applying the same symbol to all values.
Change the default symbol first and then click add values. The symbol is the same for the added values.
Grouping Values
Select desired values, right click and selectGroup Values.
Map LayoutBest Practices & Tips
TALDOGS
T - TitleA - AuthorL - LegendD - DateO - OrientationG - GridS - Scale
This acronym will help you remember what to include on a map.
Source: South Carolina Geographic Alliance
Make title logical and succinct
On thematic map, include name of area and main subject
2010 Census Population, Bernalillo County, NM
T = Title
Organization or person who made map May want to include logo, department
and contact information
Prepared by:
A = Author
Explains map symbols Clear and legible
L = Legend
Date map was created or date of original data
You may have multiple dates for data and you could include this in the legend If you had DOQQ imagery from 2005 and
census data from 2010
D = Date
Maps in the United States are generally made with North at the top of the map and South at the bottom
Some specialized maps are oriented differently
Include a north arrow
O = Orientation
Please don’t use this one!
ArcMap can automatically put coordinate system grid around map
A “location map” (overview map) also works well
May not be necessary, evaluate the use on your map and decide what is best
G = Grid
Scale is a ratio that relates a unit of measure on a map to some number of the same units of measure on the earth’s surface.
S = Scale
Disclaimer
Does your office have one? RGIS.unm.edu
▪ The material on this site is made available as a public service. Maps and data are to be used for reference purposes only and the Earth Data Analysis Center (EDAC), Resource Geographic Information System (RGIS) and The University of New Mexico are not responsible for any inaccuracies herein contained. No responsibility is assumed for damages or other liabilities due to the accuracy, availability, use or misuse of the information herein provided. Unless otherwise indicated in the documentation (metadata) for individual data sets, information on this site is public domain and may be copied without permission; citation of the source is appreciated.
Ability to wrap text in legend! Legend Properties, Layout tab, Text
Wrapping.
Legend – ArcGIS 10.1
ArcMap will automatically add extent indicator ArcMap can also automatically generate
Leader lines, but it’s best to put those in by hand.
Extent Indicator
Add Extent Indicator in ArcMap Steps to inset Extent Indicator Go to Data frame properties and Extent Indicator
tab Decide which Data Frame will have Extent
Indicator. Right click on inset data frame, go to Extent
Indicator tab. Select main map and Click right arrow. Can change color and line thickness under Options, Frame.
If have multiple Extent Indicators you may want to use different colors to help viewer identify which Extent Indicator corresponds to which inset map
ArcMap Options
Can change whether youzoom in or out with scroll wheel on your mouse!
Set relative paths, so if you move your data ArcMap can find it again.
FEMA Map Service CenterTake advantage of someone else’s server
GIS Data
NFHL
Data Download
Download NFHL GIS Data
Web Services - Layers
Layers in the public NFHL GIS services:Use the numbers shown below when referencing layers by number.0. NFHL Availability1. LOMRs2. LOMAs3. FIRM Panels4. Base Index5. PLSS6. Toplogical Low Confidence Areas7. River Mile Markers8. Datum Conversion Points9. Coastal Gages10. Gages11. Nodes12. High Water Marks13. Station Start Points14. Cross-Sections
15. Coastal Transects16. Base Flood Elevations17. Profile Baselines18. Transect Baselines19. Limit of Moderate Wave Action20. Water Lines21. Coastal Barrier Resources System Area22. Political Jurisdictions23. Levees24. General Structures25. Primary Frontal Dunes26. Hydrologic Reaches27. Flood Hazard Boundaries28. Flood Hazard Zones29. Submittal Information30. Alluvial Fans31. Subbasins32. Water Areas
Web Services - REST
ArcGIS REST Service The ArcGIS REST service provides direct
access to NFHL spatial information through ESRI applications such as ArcGIS Desktop or ArcGIS Online. This service supports mapping, data, and query requests.
https://hazards.fema.gov/gis/nfhl/rest/services/public/NFHL/MapServer
Web Services - REST
URL
Web Services - REST
Can now add to ArcMap
Web Services – WMS & WFS
The NFHL Web Mapping Service provides an OGC-compliant protocol for obtaining map images and querying feature information.
Web Services – FEMA GeoPlatform
Web Services – FEMA GeoPlatform
PanelsLOMAs
GIS Help Desk
Do you have any GIS questions? I have ArcGIS, will answer questions!
Questions
Shawn L. Penman, PhD, CFM, [email protected](505) 277-3622 ext 227