«l for the Digital Shoreline Analysis System (DSAS) version 3.2 Extension for ArcGIS v.9.0 Part of USGS Open-File Report 2005-1304 l a i r Table of ...»
User Guide & Tutorial for the
Digital Shoreline Analysis System
(DSAS) version 3.2
Extension for ArcGIS v.9.0
Part of USGS Open-File Report 2005-1304
Table of Contents
1. Title Page 17. Transect Notes
2. Table of contents 18. Recalculating Transects
3. About DSAS / System 19. Updating intersect table /
requirements DSAS toolbar buttons
4. Installing / Required 20. Transect field descriptions Inputs / Shoreline Data
5. How to append (files) (EPR, JKR, LRR)
6. Generating a baseline 22. Weighted Least Squares (approach 1) (WLR) / binary limitations
7. Baseline continued 23. Least Median of Squares (approaches 2 & 3) (LMS)
8. Baseline flow direction 24. Supplemental statistics (LSE, WSE; LCI, WCI)
25. R-squared statistic
10. Default Parameters (LR2, WR2) (general, transect)
26. Intersect field descriptions
11. Setting Transect / viewing intersect points Parameters
27. Distance field descriptions
12. Simple and Smoothed Baseline Transects 28. Troubleshooting
13. Baseline & Shoreline 29. FAQ parameters
30. Transect – IntersectImporting ArcView Distance attribute table link transects
31. Baseline Field
15. Casting Transects / requirements shoreline.log file / Editing
32. Shoreline Field Transects Requirements
16. Transect Casting Order
33. Contact Information About DSAS The Digital Shoreline Analysis System (DSAS) is an extension that enhances the normal functionality of ESRI ArcGIS software, and enables users to calculate shoreline rate-of-change statistics from a time series of multiple shoreline positions. The extension was designed to aid in historic shoreline change analysis. DSAS is also useful for datasets that use polylines as a representation of a feature’s position at a specific point in time, such as the forward limit of a glacier, river channel boundaries, land use and land cover maps.
DSAS works by generating orthogonal transects at a user-defined separation and then calculates rates-of-change and associated statistics that are reported in an attribute table. The DSAS tool requires user data to meet specific field requirements. The steps and processes to conform to these requirements are explained in this guide for reference.
• ArcGIS v.9.0 with Microsoft.NET framework v.1.1 installed
• Sample Data or other available shoreline data (meeting field requirements as described on pp.31-32).
NOTE: A version for ArcView 3.x exists for those without access to Arc 9.0 (http://woodshole.er.usgs.gov/project-pages/dsas/). The link can be found under the Previous Version heading.
You need Microsoft.NET framework v.1.1 in order to run the DSAS extension.
Please go to: http://www.microsoft.com/downloads Type “.NET framework v.1.1” in the keywords section of the search to locate and download the redistributable package.
Installing DSAS The DSAS ArcMap extension includes a setup wizard that guides users through the steps necessary to install the program.
Unzip the program and double-click the DSAS Installer.msi Windows Installer Package. Once complete, the shoreline toolbar will be opened when ArcMap is launched.
Note: In ArcMap, go to Tools - Customize - Shoreline Toolbar (if it does not turn on automatically) Required inputs
1) Sequential time series of vector shoreline positions These are just some of the examples from which vector positions
can be digitized:
· DOQQ aerial photographs · NOAA T-sheets · USGS quadrangle maps · LIDAR derived shorelines
2) User-created reference baseline The baseline is created by the user and serves as the starting point for generating transects. The DSAS extension generates transects that are cast perpendicular to the baseline at a userspecified spacing alongshore. The transect/shoreline intersections are used by the program to calculate the rate-of-change statistics.
1) Assign appropriate attribute fields to the shoreline data (refer to p.32 for details).
2) Append multiple shoreline files into a single feature class (see following page for instructions).
How to append (files):
1) Confirm that all shoreline files have the same spatial reference and feature type requirements (refer to p.32 in this tutorial).
2) The append tool will add the multiple shapefile/coverage files into one of the existing files (Hint: it is a good idea to first make a copy of the file you will append to and rename the copy as the combined shoreline file, such as “shorelines” so that you have a backup of your original data).
3) Open the Append tool from ArcToolbox (Data Management Tools - General - Append)
4) Add all shoreline shapefile/coverage files to the Input Features list in the Append window.
5) Designate the copied “shorelines” feature as the Output Features Creating a baseline The baseline is the starting point for all transects and is therefore one of the most important components of the shoreline change analysis process. Its shape and relative location to the shorelines impacts the rate calculations determined by the transect/shoreline intersections. The baseline must be contained in a single shapefile (and therefore is a single feature class once imported into the geodatabase). The user should take the time to manually edit and smooth the baseline based on their particular study area.
*The baseline can be created either onshore or offshore from the shoreline data.
Three ways to create a baseline:
1) Start with a new shapefile
2) Buffer a shoreline
3) Use a pre-existing baseline ***You must also assign attributes to the baseline (refer to baseline field requirements on p.31.
Approach one: Start with a new shapefile Create a new polyline shapefile using ArcCatalog and then add it to the ArcMap project. Begin an edit session on the new baseline file and manually draw and edit the line using standard ArcMap editor tools (refer to the ArcGIS Desktop Help menu for further instructions; Keywords: lines, vertices, moving features).
Approach two: Buffer a shoreline Generate a baseline from ancontinued of the existing shoreline. Select Baseline offset one of the shoreline segments (the most landward if onshore or seaward if offshore shoreline will often work best).
Make sure you specify a distance that will offset the resulting buffer entirely landward or seaward of all other shoreline positions. Refer to the ArcGIS Desktop Help menu for more detailed information on how to: 1) create a buffer and isolate it in a separate annotation group from the shoreline features, 2) convert the polygon buffer to a polyline and 3) split and remove the unwanted segments (Keywords;
buffering selected graphics, copying features, splitting features, polygon to line).
Approach three: Use a pre-existing baseline
This is beneficial if a baseline was previously made and stored for future studies.
NOTE: The baselines cannot contain field names that will conflict with the DSAS extension. Check field requirements on p.31 for conflicts.
Baseline “flow” direction In previous versions the user was required to manually adjust the “flow” direction of each vector in the baseline feature class so that all baseline segments had the first vertex at the end closest to the last vertex of the previous segment. Setting the line symbology to arrows enabled visualization of this flow direction.
DSAS is now set up to automate this process. By default this functionality is turned OFF. To activate, just check the “Flip Baseline Orientation” box at the bottom of the Cast Transects window before clicking OK to cast transects. Flow direction will be governed by the first baseline segment (ID=1; see p. 31).
Define Coordinate System
The spatial reference for both the shoreline and baseline files must be set in order for DSAS to accurately calculate the shoreline change statistics.
Note: DSAS requires the data to be in meter units in a projected coordinate system, such as UTM or State Plane (ArcGIS Desktop Help keyword: coordinate systems, projections).
Once a geodatabase has been created, the data can be imported as individual feature classes into a geodatabase within ArcCatalog (ArcGIS Desktop Help keyword: geodatabases importing data).
Default Parameters Default parameters button on Shoreline Toolbar
1. General Parameters Before transects are generated several parameters can be set and saved in the default parameters windows. The user must specify which feature classes are to be used as the baseline and shoreline layers as well as the accuracy and date fields (which are further explained in the statistics section on pp. 21-25 in this tutorial).
If no Accuracy field value exists for a specific shoreline, a default value must be used. The user must specify this default value under the “Set data accuracy” section.
In previous versions of DSAS the confidence interval (CI) was 90%.
DSAS now allows the user to choose the confidence interval from a drop-down list of options (90%, 95%, 98%, 99%, 99.8% or 99.9%).
The chosen value will be used for calculating the supplemental statistics (see p.24 for more information).
2. Set Transect Parameters:
The user must specify the spacing between transects along the baseline as well as the length of the transects for both simple or smoothed baseline casts (see next page for more information regarding smoothing distance).
DSAS computes the shoreline change statistics on the generated transects. All transects are cast from the baseline and intersect the multiple shoreline features. The transect layer’s attribute table provides the rate-of-change statistics.
In the simple transect above, curves in the baseline may result in some transects being cast at undesirable orientations.
The smoothed baseline option creates a supplemental baseline at the user-specified distance (with the transect being at the midpoint). This smoothing parameter is then used to determine the orientation of the transect (compare orientation of the middle transects in the simple and smoothed baseline examples above).
There will be little to no difference in transects that occur along straight sections of baseline (compare first and last transects in examples above).
Note: Both casting methods use the same calculations to generate rate-of-change statistics.
3. Baseline parameters:
The baseline can be drawn off-shore, on-shore or can be a combination of both. By checking off-shore, rate calculations will be determined assuming transect origins are seaward of shorelines. The casting direction will be determined by the default parameters described on the previous page. Onshore transect origins are considered to be landward of the shorelines in rate calculations.
If baselines are drawn both landward and seaward of the shorelines choose both. Two additional fields must exist in the baseline attribute table (see p.31) to specify the location of the specific baseline segment with respect to the land, and the appropriate casting direction to intersect the shorelines.
This preference is not intended to be switched during a project and should only be set once. The chosen baseline parameter adjusts the reported statistics for positive and negative values to correctly indicate accretion and erosion.
4. Shoreline parameters:
In some instances, a transect may intersect a shoreline segment multiple times (for example, if backshore features are present). The user is able to specify which intersection to use under the Shoreline parameters section.
Importing ArcView transects A stand-alone utility has been created to import transects that were created in DSAS 2.0 (ArcView 3.x) so that they can be used within DSAS 3.1.
This import tool will create a feature class for the existing transects within the Geodatabase specified by the user.
NOTE: the geodatabase must be created before attempting to import!
The statistics will need to be updated using the recalculate button (see p.18). This import utility will be useful in situations where extensive editing of the transects was done using the previous version of DSAS software.
Once the transects have been imported and recalculated they will be updated with all improvements and modifications made to DSAS since the 2.0 release.
Please refer to the DSAS project page for information on how to download and use the stand-alone Import Utility.
http://woodshole.er.usgs.gov/project-pages/dsas Casting Transects Once the default parameters have been set, transects can be cast.
The user must specify the location of the geodatabase where the resulting transect and intersect files will be stored.
The user is able to select either simple or smoothed baseline casts for newly generated transects (whose length and spacing parameters were specified in the default parameters window described on p.11).
Editing Transects Transects can be moved, changed, deleted or otherwise edited individually using standard ArcGIS editor tools. Once changes have been made and saved, rates of change for the transects can be recalculated to update the transect and intersect attribute 15 tables (ArcGIS Desktop Help keyword: vertices, moving).
Transect casting order The user has control over the order in which transects are cast alongshore. If multiple baseline segments exist, the casting order will be determined by the ID value assigned to each baseline segment (if only one baseline segment exists, assign it a value of one).
If a baseline segment is assigned an ID value of zero, no transects will be cast.
To keep transect numbering in sequence, assign sequential ID numbers along the baseline. The transect attribute table will indicate which baseline segment the transect was cast from in the baselineID field (see p.20 for further description).