What are data databases and generated products?
In addition to supporting the search and retrieval of PDS data products, ODE supports the concept of “Data Databases”. A data database is a database that store the actual science data from the PDS data products in a searchable database. The reason for this is to allow users to find science data for particular regions or parameters that are not easily handled with the data product structure. The most obvious one is when the data products are stored in time-sequence chunks such as the data collected during a portion of an orbit. But users may want to get all the data from the instrument that covers a particular area of the surface or have a particular parameter value.
Currently ODE supports data databases for the following data sets/product types:
Although each data database is somewhat different, there are several common elements. Each data database takes the data records from the PDS science data products and organizes them into a searchable database. Then each has a “Query Tool” that allows a user to query this database and products one or more derived products. Currently, ODE supports several types of derived products.
ASCII and CSV Tables – these are ASCII text files consisting of a set of records organized as one record per row. Each record has a set of fields separated by columns or by commas. The CSV files can be read into tools such as Excel. The record and field structure is unique to the data bases and its science data product. Each ASCII or CSV file is generated with an associated PDS label file. Please see the label file for a description of the fields.
The Shapefile output contains individual location-based data records organized in a format suitable for loading into tools such as ESRI’s ArcGIS or JMars. Typically the data consists of in a points – topography data have lat/lon points with an altitude, sensor readings have lat/lon points with one or more values at that location. The Shapefile consists of four or five individual files (See section 4.16) which should all be downloaded and placed together in the same directory.
The Binned Image is a cylindrical projected map where the left edge is the westernmost longitude queried, the right edge is the easternmost longitude, the top edge is the maximum latitude queried and the bottom edge is the minimum latitude queried. Each pixel has the image resolution of a by b in which a represents the longitude range divided by the width in pixels, and b represents the latitude range divided by the height in pixels. Each pixel is generated by averaging the attitude of each measured point (such as topography or radiance) that lies in its range (note: a better pixel value calculation would be block median but average is for performance – users desiring block median should download the points in an CSV table and directly process into an image).
There are several options involved in binned images. The first is the coloring. One can generate either a color or grayscale image. The value is based on a min/max range of values. The min/max range can be “global” or “local”. Global range uses the min/max values from the entire planet. Local range uses the min/max values for just the area covered by the binned image. For example, a MOLA PEDR binned image can be colored by the min/max topography range for all of Mars (Global) or just the area covered by the image (Local). Global coloring is useful for comparing images from different locations. Local coloring is usually a higher contrast and is useful for picking out features. Colored images are three band RGB images. Greyscale images are one band images. Binned images include a small image that shows the color or grayscale range.
In addition, there are several possible image formats. One can get PNG, JPEG, ENVI, GeoTIFF, GeoJP2000, and KMZ formats. The JPEG includes a JPW file which gives basic coordinate information. The ENVI, GeoTIFF, and GeoJP2000 files are map projected.