LOLA RDR Query Page

Lunar ODE offers a LOLA RDR Query tool. The Lunar Reconnaissance Orbiter’s Lunar Orbiter Laser Altimeter (LOLA) instrument provides a series of laser of altimetry measurements across the surface of the Moon. See "About Data Databases".

The newer ODE LOLA RDR query tool V2.0 supports larger queries. It will email results to users after query completion.

LOLA offers two key altimetry products – the RDR and GDR products. LOLA RDR products are sets of individual altimetry readings organized along the spacecraft orbit track. The GDR products are RDR products assembled into global grids referenced to Moon' center-of-mass, with resolutions of up to 1/128 degree per pixel. These will meet many users’ needs and should be reviewed prior to using the RDR tool.

The LOLA RDR Query Tool provides a searchable database of the individual RDR measurements. The LOLA RDR tool allows searches of LOLA RDR points based on Latitude/Longitude range, altitude, UTC observation time, and PDS Product ID pattern. Results can be saved as Formatted CSV files, ESRI Shapefiles or Binned Images.

A note on how the LOLA RDR query tool works with location. LOLA is a pulse detection time-of-flight altimeter that incorporates a five-spot pattern that measures the precise distance to the lunar surface at 5 spots simultaneously, thus providing 5 profiles across the lunar surface (Figure 6). LOLA fires at a fixed, 28-Hz rate, so that for a nominal 1600 m/s ground track speed there is one shot approximately every 57 m. At a nominal 50-km altitude, each spot within the five-spot pattern has a diameter of 5 m while each detector field of view has a diameter of 20 m; the spots are 25 meters apart, and form a cross pattern canted by 26 degrees counterclockwise to provide five adjacent profiles.

Figure 6 - LOLA Pattern

LOLA RDRs consist of a set of frame records, each with up to 5 valid individual altimetry measurements (channels) in a small cluster. Each individual altimetry measurement has a lat/lon surface location in Planetocentric, positive east 0..360 degree longitude coordinates. Due to noise, some individual altimetry measurements in a frame may not be valid. All frames used in the LOLA RDR query have at least one valid individual altimetry measurement. Each frame has a single lat/lon surface location, normally the center individual altimetry measurement unless that measurement is invalid. If the center measurement is invalid, then the first valid measurement is used for the frame surface location. LOLA RDR queries are based on frame locations. This means that individual altimetry measurements whose frame location is outside the query area but whose individual surface measurement is inside the query area will not be included in the results (see Figure 7). Users concerned about these edge measurements should query with a slightly larger area than their area of interest.

This same issue can impact the point count returned by the Query tool. The point count will return a count of valid individual measurements for each frame in the query area. However, as noted above, a very small number of these measurements are actually outside the query area. These measurements will not be included in the point-oriented results such as the simple Topo CSV, the point CSV, the binned images, or the shapefiles. Thus the actual number of measurements in these products may be slightly less than the total provided by the Query tool.

Figure 7 - LOLA RDR Query Tool Pattern

The LOLA RDR Query Tool has four steps. First, a latitude/longitude range must be specified. A small range is recommended due to the quantity of data points. Second, additional filtering parameters such as PDS Product ID, data point observation altitude, and observation UTC time can be specified. Third, the result count must be previewed before generating any output files. If the data point count is less than or equal to 6 million points, you can proceed to generate and download the desired result files. The forth step is to generate your query results as Formatted CSV files, ESRI Shapefiles, or Binned images. These files can be downloaded individually or in compressed format from the page.

Step 1. Select Data Point Latitude/ Longitude Range (Required)

Use this feature to filter your product data points based on their planetocentric latitude / longitude coordinates. The planetocentric coordinate system is a right-handed system with the origin at the center of mass of the Moon. The latitude is the angle between the equatorial plane and a vector connecting a point on the surface and the origin of the coordinate system. Latitudes are positive in the northern hemisphere and negative in the southern hemisphere. Longitude increases to the east. The Range can be previewed by clicking the "Show Area On Map" button.

Latitude/Longitude range may be entered in two ways: via a feature; or directly enter a range. One can select a location via USGS named features. Select the feature type, then the feature name. This will set the latitude / longitude coverage area. The other option is to directly enter a maximum latitude, a minimum latitude, an westernmost longitude and an easternmost longitude in the boxes provided.

A note of feature usage: some features are point features. If used as is, only those RDR points lying directly on the feature will be found – a rather unlikely case. Users may want to adjust the lat/lon range in the “directory specific a latitude and longitude coverage area” range by padding the area around the point feature.

Step 2. Set Additional Filtering Parameters (Optional)

This section of the search form contains optional fields for filtering by the PDS Product ID or Partial PDS Product ID, specific altitude or altitude range, specific orbit number or an orbit number range, specific UTC observation time or range, and specific channels.

Step 2 A. Select a Product ID or filter by a partial Product ID (Optional)

This section allows you to select an individual data product via its Product ID or, more commonly, select only those data products who’s ids match a wildcard string. Example: entering “LOLARDR_0011N” will only return LOLA RDR points from that specific product. Entering “LOLARDR_0*” will return LOLA RDR points from products with Product ID’s of that pattern.

Step 2 B. Filter by Altitude (Optional)

This section allows you to filter data points by altitude in meters for specific topographical ranges. The maximum and minimum ranges available are the default values.

Step 2 C. Filter by Orbit Number (Optional)

This section allows you to filter the returned data by the spacecraft orbit numbers. The minimum and maximum orbits available to be queried are displayed in the section. An individual orbit can be selected by only populating the minimum orbit field or entering the same value in both min and max orbit fields. Otherwise, the range limitations are used when both minimum and maximum values are entered.

Step 2 D. Filter by UTC Time (Optional)

Each LOLA RDR point has an observation UTC time. Enter a single UTC time, partial UTC time, or a UTC time range to filter the search results by the observation time. The maximum and minimum UTC range of the data is listed for reference.

Step 2 E. Filter by Channels (Optional)

The LOLA instrument uses 5 channels to acquire data. The search page defaults to using all channels, but you can modify the results by deselecting undesired channels.

Step 3. Preview Results Count

There can be millions of points in the LOLA RDR point database. This required step will display the number of data points that match the entered search criteria. If the data point count is less than or equal to 6 million points, you can proceed to generate and download the desired result files.

Also note, that any change to the search criteria will clear the results and require a re-query of the results count.

If the count is over 6 million points, the buttons to generate result files will be disabled and a message indicating that the point count is too large will be displayed. You can contact ode@wunder.wustl.edu for large volume special requests.

Step 4. Request Results

After successfully previewing the result count, there are four choices of formats for the search result output. The results may be saved in a formatted CSV text format, Shapefile format, or as a Binned Image. See below for full descriptions of each format. To create the files of the desired format, simply click the “Generate Files” button for the format. It may take a few minutes for the files to be created. A message will be displayed that indicates the files are being created. After the result files have been created, you can download the files individually or grouped as a zip, tar, or tar.gz file.

The frame per row CSV table is identical to the output from the LOLA software included in the LOLA archive. Each frame per row CSV file is generated with an associated PDS label file. Please see the label file for a description of the fields.

The point per row CSV/ASCII table provides a list of measurements with one measurement per row. Each point per row CSV file is generated with an associated PDS label file. Please see the label file for a description of the fields.

The simple topography CSV/ASCII table provides a list of measurements with one measurement per row. Each row contains the point UTC, Lat/Lon location, and Topographic value. Each simple topography CSV file is generated with an associated PDS label file. Please see the label file for a description of the fields.

The Binned Images consist a set of average topography 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 RDR point 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). The binned images includes several additional formats – see the included README file or section 4.19).

The Shapefile output contains the queried RDR points in a point Shapefile suitable for use in GIS tools such as ESRI’s ArcGIS or JMars. The Shapefile consists of five individual files which should all be downloade and placed together in the same directory. The LOLA RDR Query tool produces two types of Shapefiles – a “POINT” and a “POINTZ” shapefile. The POINTZ shapefiles have an “_z” name extension. POINT shapefiles store the topography points with a Lat/Lon coordinate and a Topography attribute field. POINTZ shapefiles store the topography points with a Lat/Lon/Z coordinate (and a Topography attribute field like the POINT shapefiles). POINTZ shapefiles work well in 3D aware tools such as ESRI’s ArcScene tool. However, not all GIS tools (such as JMars) understand POINTZ so users should use the POINT version. ArcScene users can use the POINT shapefiles by setting the base height to the Topography attribute field value:

Add the POINT shapefile to ArcScene
Right click the shapefile layer, and select Properties
Select the Base Heights tab
Select the “Use a constant value or expression to set heights for layer:”
Select the Calculator next to the field and select Topography
Remember to adjust vertical exaggeration via right click on the Scene Layers (Since Topography attribute uses the unit of meter, which is different from the unit of degree for Lat/Lon, the vertical exaggeration factor is recommended to be some number between 0.0005 and 0.001 for better visualization of 3D.)