NHD SWaMT Help System

• Map Tools Overview
• Using the Search Tool
• Changing How Layers Display on The Map
• Submitting Feedback Procedures

The Surface Water Maintenance Tool website includes an interactive web mapping application. You have control over the area displayed and decide which data layers are displayed on the map. This page contains a few user tips and guidance on best practices when submitting "maintenance tickets" requesting updates to features in the National Hydrography Dataset.

Note: This tool is best viewed using Internet Explorer and has been optimized for a 1024 x 768 screen resolution. The current "timeout" period is set to 30 minutes. If the period of inactivity exceeds this value, the user is required to log back in.

The navigation tools on the left side of the map tools enables the user to Zoom In (-) or Zoom Out (+), to "Pan" (represented by a hand icon), and to Zoom Full, in order to change how the map is centered.

NOTE! The visibility of the remaining tools depends on which of the three "wizards" are chosen, e.g.; 1) General Feedback; 2) Create New Feature; or 3) Update Existing Feature.

These tools are:

Error Box: For drawing a bounding box that contains errors for general comments.

Sketch Line Tool: For delineating the updated 1 dimensional (1D) stream geometry.

Sketch Polygon Tool: For delineating the updated 2 dimensional stream and lake/pond geometries.

Select Tool: Allows the user to specifically identify a "Stream" or "Waterbody" that gets attached to the maintenance ticket. Requires the user to select EITHER the "Stream" or "Waterbody" radio button.

Clear Tool: Clears ALL sketches of new or updated features.

If the NHD feature in question is near a 'place' such as an Airport, Bridge, Cemetery, Church, Dam, Island, Lake, School or Summit etc. use the Placename Search tool to zoom to that area. The search tool works on place names in the national Geographic Names Information System (GNIS)1.

To zoom to a feature:

1) Enter the exact spelling of the placename, if known; or

2) If the exact spelling isn't known, use the wildcard character '%'. Don't use the following common search operators: 'AND'; 'OR'. For example:

• hunt% - where the result must begin with the letters 'hunt', e.g., 'Huntington Falls Dam'.
• %hunt - where the result has the letters 'hunt' anywhere within the string and can end with any letters, e.g., 'Alice Hunt Cemetery' or 'Huntington Falls Dam'.

3) Check the desired feature, mouse over the name and Right click to either "Zoom to" or "Pan to" the feature.

1The GNIS was developed by the U.S. Geological Survey for the U.S. Board on Geographic Names. The GNIS is the official repository of domestic geographic names data.

To view/hide layer symbology, click on the 'treeview' (+/-) button.

To add or remove layers from being displayed, simply click the check box next to the layer. The map will automatically redraw. After clicking the check box, allow the map image to refresh before checking a second layer. Please note that some of the layers are scale dependant and will not display at all scale ranges. See the table below. This means that as the user zooms in and out, certain layers will be enabled or disabled based on their set scale range. The check box next to disabled layers appears tan rather than white, and a check mark in it will appear as a slightly darker tan, rather than black.

Feature & Label Scale Thresholds:

Layer Name	Min Scale	Max Scale
100 foot contours	1:50,000	1:100,000
50 foot contours	1:10,000	1:50,000
5k ORTHO Photo Year		1:24,000
DEM Data - DEM24	1:100,000	1:10,000
DEM Data - HILSH24	1:100,000	1:10,000
Landmarks	1:24,001	1:200,000
Roads: Driveways		1:10,000
Roads: E911 Road Names		1:24,000
Roads: Roads - All (public)		1:50,000
Roads: Roads - Major 1	1:50,000	1:500,000
Roads: Roads - Major 2	1:50,000	1:100,000
Roads: Roads - Private (E911)		1:50,000
Roads: Roads Shields
County Boundaries	1:50,000
State Boundaries
Town Boundaries
VHD - 2D Streams & Rivers		1:125,000
VHD - Lakes & Ponds		1:125,000
VHD - Streams		1:125,000
VT Imagery & Topo: VMP Orthos (1:5k: 1994-2000; 2006)		1:10,000
VT Imagery & Topo: NAIP 2003(1:40k)		1:10,000
VT Imagery & Topo: Topomaps (1:24k)	1:10,000	1:24,000
WBD Subbasins

Overview

The SWaMT tool is built around the Wizard concept where the user selects one of three wizard options to submit feedback via a “maintenance ticket”. Next, the user follows each step of the wizard to a logical conclusion (submittal of the ticket). The "General Feedback", "Create New Feature" and "Update Existing Feature" wizards afford feedback on a descending number of features, while the level of detail increases, respectively. This is accomplished by attaching shapefile(s), image attachments or drawing an "error box", to sketching individual features in a smaller area where they are either absent or mis-represented in the existing dataset.

The need for maintaining and updating geospatial data is an ongoing process required to mitigate existing and evolving errors that stem from a variety of sources. The section "Maintenance vs. Error" below provides a broad overview of this important issue.

 

General Procedures

While only one ticket can be submitted at a time, the user has the opportunity to submit as many additional tickets as needed. For complicated areas with a combination of changes to features, i.e., to be deleted, added or relocated, it may be necessary to use a combination of the wizards. Match your feedback requirements with one of the three wizards.:

• General Feedback:
• If you have an existing shapefile(s) or image file(s) that reflects the new or updated feature(s) this option allows you to attach it.
• If there are a number of features with geometry errors in close proximity to one another that you can draw an "error box" around. For missing features it is better to explicitly sketch them with the "Create New Feature" tool than to describe them unless their absence is abundantly clear on the map.
• When attaching shapefiles of updated features, include the entire feature(s) even if only a small portion was updated.

• Create New Feature:
• If the feature(s) is not currently represented in the NHD, sketch either lines or polygons to represent them.

• Update Existing Feature:
• If the geometry of either a Stream or Waterbody feature is poorly represented or has changed over time, i.e., updated imagery has become available showing the change, select the feature before sketching the new geometry.
• First, choose the "Select" tool to select a feature(s). Next use the appropriate sketch tool to create the updated feature geometry. Selecting the feature first allows information about that feature to be captured automatically and included with the maintenance ticket.
• If you have a combination of "delete" and "add" suggestions, separate them into two maintenance tickets by selecting all "deletes" first and submitting before then selecting all "adds" and either sketching or adding a shapefile in the second ticket.

Errata

Here is a list of both characteristics and limitations of the tool:

• There's no "Back" button? In lieu of a back button simply click on the "Begin Feedback Wizard" to choose another wizard option or to start the same wizard over again.
• The "Clear" button: Selecting this button wipes away ALL sketched features, not just the most recently added one.
Maintenance vs. Error

While human error can certainly be the source of "error" at the point of initial data development, there is a distinction between actual "source error" and "relative (temporal) error" for features as dynamic as surface water when viewed using updated imagery. The former is simply an error, while the latter is actually not an error at all, but maintenance required by time! The figures below demonstrate how well the initial river delineation complies with its original source digital ortho-photography and how much it has changed in ten years. To date, there has only been one update to the source imagery (2006) in Vermont. As a result, areas labeled “Ortho Photo Year 2006” are likely to have more discrepancies than other areas.

This comparison underscores the fact that updates to source data and/or technological advancements have and will continue to play a big role in keeping information up-to-date. It also demonstrates that feature error is relative and in many cases is more accurately expressed as a feature in need of maintenance.