Scatter Points

Scatter Points

Scatter points may be used to define spatially-explicit model inputs for the following parameters:
- hydraulic conductivity
- aquifer top or bottom elevations, or partial penetrating feature elevations
- recharge
- prescribed head
- effective porosity
- specific storage and specific yield

Input Data

Users may enter scatter point data directly into the table, load data from a file (ASCII/.txt format), or load data from a shapefile.

NOTE: Importing very large datasets (many scatter points) into the Maps Display and Working Area may significantly slow down the modeling page response time. Use the Show Points / Hide Points buton (see below) to avoid this issue once the data have been imported.

Table / Txt Format

Each observation should have its own line (row). If loading data from a file, the 1st line (row) should include the header line shown in the table:

SPID, x(Lon),y(Lat),SPvalue, Icolor

- SPID = scatter point ID
- x(Lon) = x-coordinate (e.g., longitude)
- y(Lat) = y-coordiate (e.g., latitude)
- SPvalue = scatter point value (e.g., aquifer bottom elevation, hydraulic conductivity, porosity, etc.)
- Icolor = scatter point color (when shown in display)

Seperate record entries with ','.

The expected units for SPvalue are:

- hydraulic conductivity => m/d
- aquifer top or bottom elevations, or partial penetrating feature elevations => m
- recharge
- prescribed head => m
- effective porosity => [dimensionless decimal]
- specific storage => 1/m
- specific yield => [dimensionless decimal]

Shapefile Import

Vector (point) data stored in a shapefile format can be imported by selecting 'From a shapefile'. More details are available once this option is selected.

Projection System

The deafult projection system is longitude-latitude. Select the radio button next to 'Same as model PRJ' to use the same projection system assigned in the domain attributes menu (see Other subtab). Users may load their own projection file for the scatter points (if it is different from longitude-latitude or the projection system being used by the model) by selecting the radio button next to 'Load PRJ File'.

Interpolation Method

Two options are available for spatial interpolation: Inverse Distance Weighting, or IDW; and algebraic regression (Regression).

To implement IDW, choose ‘Inverse Distance’ from the drop-down menu next to 'Interpolation Method'. There are two parameters that need to be set when using the Inverse Distance interpolation method: 1) the power parameter, p, in the weighting function (typically p=2), set in the ‘Power’ field ; and the number of nearest scatter points to use for interpolation, set in the ‘Nearest Pts’ field.

To implement regression, choose 'Regression'from the drop-down menu. Choose a linear, bilinear, or quadratic scheme and indicate the number of nearest scatter points to use for interpolation, set in the ‘Nearest Pts’ field.

Map Data Markers

Once the scatter point data have been entered/imported to the table display, click the ' Add Marker' button to create data markers that can be shown/hidden on the Google maps/Bing maps.

Once the data markers are created, use the 'Show Points'/'Hide Points' button toto show or hide those markers in the Map Display and Working Area.

Removing Data / Data Markers

To remove a data point(s), simple remove the line/row entry from the data table. If markers have been added to the display (see above), click the 'Hide Points' / 'Show Points' to update the map display with the updated data in the data table.

Note that the data from the table are shown as blue markers. Grey markers show the locations where data was "manually" added (by clicking on the map). Grey markers are removed from the map display the next time the user submits a model for simulation.