Transform Topics

Center and Centroids

A discussion with illustrations of the various centroid operations in the Transform pane.

Clip

Using the Clip template to cut objects using areas.  

Normalizing Topology

Examples and discussion of the Topology template for geometry fields in the Transform pane.

Topology Overlays

ESRI-style topology overlays utilize objects to manipulate other objects, such as clipping some objects by their intersection with others.

Raster Paths

The Manifold Path template in the Transform pane works with a map containing a raster image and a vector drawing that contains points, to provide Manifold implementations of classic GIS raster analytic tools, similar to those users may know from other GIS packages, such as the Distance tools in ESRI's Spatial Analyst toolset.  The general idea of such tools is to use raster data to compute solutions involving various routing (path) characteristics, such as cost, between different locations, calculating a solution for all pixel locations in a raster at once.

Viewsheds

The Viewshed transform template find those portions of a terrain elevation surface that are visible to observers located at given points and heights.  

Voronoi Diagrams

Voronoi diagrams provide a useful analytic framework in many tasks.

Watersheds

Watersheds are regions of terrain which share a common drainage.  Given a raster image that represents terrain elevations, the Watershed Areas and Watershed Lines templates create areas that show regions of common drainage, or create lines that show networks of streams into which water drains.  The Watershed Areas, Sinks template creates areas that show regions of closed drainage.

Example:  Create Watershed Areas

Create areas that show regions of common drainage.

Example: Create Watershed Lines

Create lines that show networks of streams into which water flows within a region of common drainage.

Shreve Order and Strahler Order

Systems to assign a number to each watershed area or stream line which indicates at what level it lies within the branching hierarchy of the overall drainage system.

Watershed Areas, Sinks

Create areas for regions that are sinks, that is, closed drainage basins or pits.

Upstream Areas and Lines

Given a single-channel image showing terrain elevations, plus a drawing that contains points, we can use the Watershed Areas, Upstream transform template or the Watershed Lines, Upstream transform template to find the regions from which or the stream lines by which water flows to each point.  

Watershed Prepare: Filling Sinks

Sinks are watershed drainage basins that are closed, that is, which have no outlet downstream.  The Fill Sinks transform template fills sinks in terrain elevation data based on specified criteria, which is often a sensible first step before launching other Watersheds transform templates.

Downstream Lines 

Given a single-channel image showing terrain elevations, plus a drawing that contains points, we can use the Watershed Lines, Downstream transform template to find the stream line for each point by which water issuing from the point flows further downstream.

Flow Direction and Accumulation

Given a single-channel image showing terrain elevations, we use the TileFlowDirAccumPar SQL function (the parallel version of TileFlowDirAccum) to compute flow direction and accumulation.  The function returns a table for a dual image, that is a table with fields for X and Y plus two tile fields: FlowDir and FlowAccum.  When a table has two tile fields, two images can be created from the same table, in this case one image showing flow direction and the other showing flow accumulation.

How Matrix Filters Work

An illustrated explanation of how matrix filters, like those used in various image transforms, work.