Data Subsetting and Conversion

Point Data Documentation

2 Data Subsetting and Conversion

RAMADDA provides an interactive service for point data subsetting, converting and product generation. This facility is available through the menu, e.g.: LVIS/Costa Rica.

This facility is available for both individual point data entries as well as Point collections. For collections certain products are not supported.

The subset and product form is composed of a number of sections that allow you to select what products are desired, specify subsetting information and provide information about the processing job.

2.0 Product Selection

One can select any number of point or grid data formats:

Image 1: Product Selection

Under Point Products the "Native Format" will return the data in its original format. For LAS we generate LAS 1.2. The LAS point format depends on what the original data contains (e.g., rgb, intensity, time, etc).

Note: For now we don't write out the geotiff CRS section. All coordinates are assumed to be latitude/longitude/altitude

There are 2 forms of Comma Separate Values (CSV) provided: "all fields" and "Lat/Lon/Alt". All fields will include all of the Point observation parameters. If the Point file has waveforms then you can also include the waveform values in the CSV by checking the checkbox under the section.

You can also create a variety of gridded products from a variety of grids. You select what grids you want (e.g., minimum value, inverse distance weighted average (IDW)) and you select what kinds of products you want to create.

Note: The gridding algorithms are being refined and have yet to be fully vetted. The minimum, maximum and average values are simple gridding - i.e., the point value only affects a single grid cell. The IDW average does an inverse distance weighted average within a region of grid cells.

By default the altitude is the field that is gridded. However, under Advanced Settings you can select other parameters (if available) to grid.

2.1 Subset Data

You can do both spatial subsetting and decimation. For decimation you can select a skip factor or a probability. The skip factor allows you, for example, to use every 10th point (e.g., skip=9). The probability is a value between 0 and 1, e.g., 0.3 = 30% probability that a point will be included.

2.2 Advanced Settings

There are a number of processing options you can select under Advanced Settings:

Image 2: Advanced Settings

If you chose the IDW average grid product then you can specify a radius of influence for each Point point. The radius can either be in terms of degrees or number of grid cells.

If "Fill missing points" is checked on then grid cells that had no value but are adjacent to grid cells that have values are filled with the adjoining value. No attempt is made to average or interpolate the values.

The Hill shading azimuth and angle are used for the hill shaded image product.

You can also specify the dimensions of the grid or image and the color table to use for the image product.

Note: The color table range is the min/max of the grid values.

2.3 Job Processing

When you submit a request the processing job will be run asynchronously (unless you uncheck the option under Processing Options) and you will be redirected to a Job Status page. This page will reload until the processing is complete. At that time it will display links to the data files and products that you selected. If you specified an email address then RAMADDA will send you an email notification when your processing request is completed.