Vector Importer

The Vector Importer (vpf_imp) is the NIMAMUSE application that allows you to access NIMA digital vector data in Vector Product Format (VPF) for further use in the NIMAMUSE Fusion program and in some commercial programs. The operation is simple: you identify the geographic rectangular bounds and feature types of your area of interest, and the Vector Importer extracts that data and saves it to a file in an output format of your choice. This data flow is illustrated in the diagram below.

The use of the Vector Importer (a.k.a. VPF Importer, vpf_imp) requires some basic knowledge of the Vector Product Format, and detailed knowledge of the digital vector data that you are importing. This knowledge is required because you will need to make decisions based on the VPF structure, and your thematic filtering criteria will be based on input data values.

Also included in the Vector Importer is a VPF table browser. Using this will allow you to display and data values in any VPF table (file). Again, knowledge of VPF and your input data is required. There is also a converter function in the Vector Importer that will convert vector data in ASCII format or MapInfo format to the NIMAMUSE Vec format.

Detailed steps for all three of these sessions (Import/Retrieve Features, Browse Tables, and Convert to NIMAMUSE Vec) are illustrated below. There are also some tutorials contained in [ Vector Importer Users Guide], VPFI_UG.DOC, and on-line help (during a vpf_imp session) that are available.

Digital Vector Data

Simply put, digital vector data are connected points that represent natural and cultural geographic features. Various level of spatial relationship can be represented in the vector data base. Typically, there is also descriptive data (attributes) that can be associated with a vector feature.

NIMA digital vector data in VPF are arranged in various types of relational data base tables, which are stored as files. These files hold the various types of features in VPF (area, line, point, text), and are arranged in directories, which reflect the VPF structure.

The visual display of this vector data is entirely up to the user. You make the decision on what features to display, their color, line weight, and annotations. Since VPF data is organized in layers (coverages), you can "stack" these layers at your discretion for display.

The simplified diagram below shows a simple vector data base, first as a displayed picture, then as a table. In NIMA VPF products, the coordinates are in units of latitude and longitude, and there are separate tables for area, line, point and textual data.

The Vector Importer (vpf_imp) inputs NIMA Vector Data products in Vector Product Format (VPF) and outputs features in selected rectangular areas in NIMAMUSE Vector Format or other formats.

There is a support function that allows you to browse the contents of a VPF table, and a function that lets you convert vector data in ASCII format or in Map Info format into the NIMAMUSE Vec format.

The Three Vector Importer (vpf_imp) Sessions

(1) The Feature Retrieval Session (2) The Browse Table Session (3) The Convert to NIMAMUSE Vec Session

(1) The Feature Retrieval Session

The Feature Retrieval Session can be viewed as having six major session steps:

1. Identify Your Output Format

2. Identify Your Input Vector (VPF) Data

3. Choose Your Geographic Extents

4. Retrieve Feature Types from the Input (this step is repeated for more feature types)

5. Choose Symbology for each Feature Type retrieved

6. Identify Output Filename for each Feature Type retrieved

Some Preparation Before You Retrieve Features

Before your Feature Retrieval Session begins, gather the following information:

(1) determine your output format

(2) determine the geographic extents from which your vector data will be selected

(3a) determine the VPF Library, VPF Coverage and VPF Feature Class you are interested in

(3b) determine selection criteria if you are interested in retrieving a subset of your target Feature Class

(4) make choices on the symbology (color, line weight) among all of your selected feature types

(5) choose a location (pathname) on your disk where your selected features will be saved.

Here are the output formats to choose from:

Note: OPCPlot is a general-purpose mapping program from the Minerals Management Service (MMS) and the Intergovernmental Oceanographic Commission (IOC).

A look at the Feature Retrieval Session

A typical feature retrieval session is illustrated in the pictures below. The pictures are of a sample session on a Sun computer. Other platforms will have similar looking windows with the same choices. The pictures below will match the six steps described in the Feature Retrieval section above.

Step 1: As you can see in the picture below, you begin by choosing your output format from the list under the pulldown menu selection "Options/Output Format":

Be careful when you pick your output format. You won't see verification of your choice until Step 6, where the output file extension from the table above shows up in the top line of the "Save Selected Features as ..." file selection box.

Step 2: Your input vector (VPF) data is identified from a File Selection Box:

Steps 3 & 4: Identify your geographic extents, and identify feature types from the window shown below:

Step 5: Choose symbology for each Feature Type retrieved:

Step 6: Identify Output Filename for each Feature Type retrieved:

A word about Thematic Filtering in a Feature Retrieval Session

When you identify the Feature Class in Step 4 above, the Vector Importer assumes that you want to retrieve ALL features in that class within the specified geographic boundaries. In this window, you can further limit the features you retrieve within the feature class by "thematic filtering". This thematic filtering is a way of specifying features by the values of their attributes defined in the product specification. In vpf_imp, this is implemented by using one or two "Where" clauses in the window, called up by clicking on the "Where Clause" button at the bottom of the window. As you can see in the first two pictures below, you choose an attribute from a list presented to you, choose a relationship (e.g. "equals"), and choose an attribute value that reflects your thematic filtering intent. A Retrieve Session with a "Where" clause will retrieve from the Feature Class just those features specified in the body of the "Where" clause.

In the case of two "Where" clauses, thematic filtering is enabled by specifying features by the values of two different attributes of the product. Further, you can elect to define feature retrieval by including just those features that meet the criteria in BOTH "Where" clauses (logical AND), or by including features that meet the criteria in EITHER ONE of the "Where" clauses (logical OR). A sample case of two "Where" clauses connected by a logical AND is shown in the picture below.

As you can see, successful thematic filtering requites an intimate knowledge of the Vector Product Format and of your VPF product specifications.


(2) The Browse Tables Session

The Browse Tables Session has just two steps: Identify the VFP table you wish to browse by choosing a filename, and select output browse settings for display. You can browse any table in your product's VPF data base. Large files may take several minutes to be displayed.

Choose "Browse Tables" from the "Option" pull down of the main VPF Importer menu bar to begin.

Step 1: Identify the VPF table to browse in a File Selection Box:

Step 2: Set display settings and view info about the table to be displayed:

Shown below is a sample display of a VPF table (here, an area feature table) via "Browse Tables":


(3) The Convert to NIMAMUSE Vec Session

The Convert to NIMAMUSE Vec Session is also a very simple operation: identify your input vector file as ASCII or Map Info MIF, and assign a name for the newly generated NIMAMUSE Vec output file. Choose "Convert to NIMAMUSE Vec" from the "Option" pulldown of the main VPF Importer menu bar to begin.

Next, identify your input vector data file (*.asc or *.mif) with a File Selection Box:

Finally, name your output NIMAMUSE vector data file with a File Selection Box:

Your new NIMAMUSE Vec file is now saved.


Related NIMAMUSE Documents

Vector Importer Users Guide  VPFI_UG.DOC

Raster Importer   RAST_IMP.DOC

Raster Importer Users Guide  RAST_UG.DOC


Fusion Users Guide   FUS_UG.DOC

Access and Prepare NIMA Digital Data  APNDD.DOC

Build Your Own Map   BYOM.DOC

Run Specialty Applications   RSA.DOC

NIMAMUSE 2.1 Documentation   INTRO.DOC