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Map-a-Planet: Explorer Help


Explorer

The Map-a-Planet Explorer is an online mapping browser that allows you to explore the images of the surface of a planet or satellite (moon), access information related to the area you're exploring, and order a seamless, tailor-made image map in a wide variety of image formats.

Click on regions in the Map-a-Planet Explorer screenshot below to learn more about those features.

[Screen shot of Map-a-Planet Explorer]

Map-a-Planet is driven by the USGS MapMaker engine, which generates image maps from our image data repository.


Navigation Toolbar

The Navigation Toolbar holds a collection of tools for exploring the surface of the planet or satellite you're currently viewing. Most web browsers will display a pop-up tool tip hint about what that button does when you hold your mouse cursor over the button.

Button Description
[Pan buttons] Pan Buttons: Click on one of the arrows to pan (move the view) in the direction the arrow is pointing. For example, if you click the Pan Left (left arrow) button, the new view will show you an area to the left of the original view. The pan buttons move the view half-way across the image. Grey arrows indicate the button is disabled because you've panned the view to the limit in that direction (disabled grey arrows are a lighter hue than the enabled blue buttons).
[Zoom In button] Zoom In Button: Click on the Zoom In button (the magnifying glass with the "plus" sign) to show the area around the center of the image at greater detail. This will reduce the surface area covered by half and double the resolution in the same image dimensions.
[Zoom Out button] Zoom Out Button: Click on the Zoom Out button (the magnifying glass with the "minus" sign) to show more of the area around the center of the image at lower detail. This will double the surface area covered and reduce the resolution by half in the same image dimensions.
[Full Resolution (1:1) button] Full Resolution (1:1) Button: Click on the Full Resolution (1:1) button to view the area around the center of the image at the maximum detail level of the data set. Grey Full Resolution (1:1) button indicate the button is disabled because the view is currently at the full resolution or greater (disabled grey button appears a lighter hue than the enabled blue button).
[Full Extent button] Full Extent Button: Click on the Full Extent button (the orange oval globe) to view the entire planet centered on the current center of the image. Grey Full Extent button indicate the button is disabled because the view is currently at the full extent (disabled grey button appears a lighter hue than the enabled button, which is shades of orange and black).
[Graticule (grid) button] Graticule Button: Click on the Graticule button (grid lines) to turn off or turn on display latitude and longitude grid lines spaced at 5° from the upper left corner of the image.
[Reset button] Reset Button: Click on the Reset button (red "stop sign" shape) to reset all the options to the default values and view the whole planet.
[Double by Lines and Samples button] Double Image Size (By Lines and Samples) Button: Click on the Double Image Size (By Lines and Samples) button (plus sign in lower left, small white square with checkerboard behind a bigger yellow square with checkerboard) to increase the image size by the number of lines and samples (width and height measured in pixels), keeping the same image extent (latitude-longitude boundaries) and increasing the resolution.
[Halve by Lines and Samples button] Halve Image Size (By Lines and Samples) Button: Click on the Halve Image Size (By Lines and Samples) button (minus sign in lower left, big white square with checkerboard behind small yellow square with checkerboard) to reduce the image size by the number of lines and samples (width and height measured in pixels), keeping the same image extent (latitude-longitude boundaries) and decreasing the resolution.
[Double by Degrees button] Double Image Size (By Degrees) Button: Click on the Double Image Size (By Degrees) button (plus sign in lower left, small white square with grid behind bigger yellow square with grid) to double the image size by number of degrees of latitude and longitude. This makes the image size roughly twice as big at the same resolution with exactly twice the number of degrees of latitude and longitude displayed.
[Halve by Degrees button] Halve Image Size (By Degrees) Button: Click on the Halve Image Size (By Degrees) button (minus sign in lower left, big white square with grid behind small yellow square with grid) to reduce the image size in half by number of degrees of latitude and longitude. This makes the image size roughly half as big at the same resolution with exactly half the number of degrees of latitude and longitude displayed.
[Order button] Order Button: Click on the Order button (shopping cart) to order the current image as a download in one of several image formats (such as TIFF, PDS, and RAW). The order form also provides a form for fine-tuning the image options. Ordering images from Map-a-Planet is free! Read more about ordering image downloads.
[Features in this Area button] Features in this Area Button: Click on the Features in this Area button (binoculars) to search the Gazetteer of Planetary Nomenclature for planetary surface features covered by the current view.
[Find Published Maps button] Find Published Maps Button: Click on the Find Published Maps button (compass rose) to search the Planetary Map Index for published maps covering the current view.
[Help button] Help Button: Click on the Help button (question mark) to view this help page.

Data Sets

The Data Sets tool box contains a list of all the data sets (types of images from different missions, different cameras, and so forth) available for the current planet or satellite you are viewing. The data set you are currently exploring is listed on a button with a dark border and brighter background and text color (the data set name is also listed at the top of the page). To explore a different data set, click the name of the data set in the list and the new image will have the same view (the same area at the same resolution) using the data set you have chosen.

[Help button]

Data Set Information: Click the small Help button (question mark) next to each data set name to view more information about that data set on the Data Sets Help page.

[Full Resolution button]

Data Sets and detail level (resolution): Not all data sets have the same maximum resolution, or detail level, so may appear blocky. Hit the Full Resolution (1:1) button in the Navigation Toolbar to view the image at the full resolution of the data set. Read more about scale and resolution.


Image Information

The Image Information box is a collapsible box containing a list of all settings for the current image. Click the arrow next to the Image Information title to open (show) or close (hide) the box. The arrow next to the Image Information title indicates if this box is open or closed -- pointing down shows it's open, pointing right shows it's closed. The images below show the Image Information box in the closed and open states.

[Image Information box is closed (hidden)]

Image Information box is closed (hidden)

[Image Information box is open (shown)]

Image Information box is open (shown)

The table below briefly describes the information found in the Image Information listing.

Title Description
Image Size

This is the dimensions of the displayed image expressed in pixels of width and height.

Resolution

This value is the image detail level expressed in pixels per degree.

Scale

The pixel scale of the image is the image detail level expressed in kilometers per pixel.

Projection

This value is the map projection of the image. For more information about map projections, see the entry for Projection in the glossary.

Bands

This describes the combination of data set bands in the image channels to be changed to create a new color combination, listed in red, green, blue channel order. For more information about the bands in the various data sets, see Map-a-Planet Data Sets. The Glossary has a definition for band.

Grid

This is the increment (in degrees) of the latitude-longitude lines (graticule) on the image, or "No Grid."

Stretch

This is the type of contrast stretch enhancement applied to the image.

North, South

These values describe the northern (top) and southern (bottom) extent of the image in geographic coordinates of degrees latitude. Values south of the equator (i.e., southern hemisphere) are expressed as negative latitude. For most map projections, the maximum latitude value is 90° and the minimum value is -90°. For the Mercator projection, the maximum and minimum allowed values are 89.990° and -89.990°, respectively.

East, West

These values describe western (left) and eastern (right) extent of the image in geographic coordinates of degrees longitude. Values may be positive or negative, and typically range between -180° and 360°.

Center of Projection

The Center Longitude of Projection is a parameter used to project the image. The default value is the center longitude of the image. For some map projections, this setting has no effect. For more information about map projections, see the entry for Projection in the glossary.


Advanced Options

The Advanced Options box is a collapsible menu containing a form for modifying the settings for the current image. Click the arrow next to the Advanced Options title to open (show) or close (hide) the box. The arrow next to the Advanced Options title indicates if this box is open or closed -- pointing down shows it's open, pointing right shows it's closed. The images below show the Advanced Options box in the closed and open states.

[Advanced Options box is closed (hidden)]

Advanced Options box is closed (hidden)

[Advanced Options box is open (shown)]

Advanced Options box is open (shown)

The table below describes each option.

Advanced Options
Option Description
Image Size

These values set the dimensions of the displayed image in pixels. The image resolution will be automatically recalculated to keep the current extent of the image within the new image size. If the aspect ratio (ratio of height to width) of the new image size is different, the extent will be extended in either the horizontal or vertical direction.

The Image Size option cannot be used in combination with the Resolution (described below).

Resolution

This value sets the image resolution (expressed in pixels per degree). The image size will be automatically recalculated to keep the current extent of the image at the new resolution. The full resolution of the current data set is noted to the right of the entry box. Using the full resolution value for this setting is equivalent to clicking the 1:1 button in the Navigation Toolbar.

The Resolution option cannot be used in combination with the Image Size (described above).

Scale

The pixel scale of the image (expressed in kilometers per pixel) is automatically calculated based on other settings, such as image size and extent. This value cannot be changed and is provided for reference.

Projection

This value sets the map projection of the image. For more information about map projections, see the entry for Projection in the glossary.

Bands

This setting allows the combination of data set bands in the image channels to be changed to create a new color combination. The band numbers are listed in three drop-down menus that are listed in red, green, and blue channel order from left to right. Changing this setting is typically only useful when a data set has more than three bands, such as the Clementine UV/Vis multispectral data set.

For more information about the bands in the various data sets, see Map-a-Planet Data Sets. The Glossary has a definition for band.

Grid

The Grid option sets the increment of the latitude-longitude lines (graticule) on the image. Set this option to "No Grid" to turn off the grid lines.

Stretch

This setting changes the type of contrast stretch enhancement applied to the image. For more information about the specific stretch options, see the description of stretch types table below.

North, South

These values set the northern (top) and southern (bottom) extent of the image in geographic coordinates of degrees latitude. Values south of the equator (i.e., southern hemisphere) are expressed as negative latitude. For most map projections, the maximum latitude value is 90° and the minimum value is -90°. For the Mercator projection, the maximum and minimum allowed values are 89.990° and -89.990°, respectively.

East, West

These values the western (left) and eastern (right) extent of the image in geographic coordinates of degrees longitude. Values may be positive or negative, and typically range between -180° and 360°. Depending on the direction of increasing longitude for the data set, one of these values must be greater than the other. A tip is shown to the right of the entry boxes. For longitudes increasing to the west, the tip west > east indicates the West (left) value must be greater than the East (right) value. Conversely, east > west indicates longitudes increasing in the eastern direction, thus the East (right) value must be greater than the West (left) value.

Center of Projection

This setting changes the Center Longitude of Projection parameter used to project the image. The default value is the center longitude of the image. For some map projections, this setting has no effect. For more information about map projections, see the entry for Projection in the glossary.

Submit Changes

Click the Submit Changes button to create a new image using the settings defined in the Advanced Options box.

The table below describes the types of contrast enhancement stretches available on Map-a-Planet.

Stretch Types
Linear/Auto The type of stretch used for auto stretch is a linear stretch. This stretch finds the minimum and maximum pixel values (often called digital numbers or DN for short) of an image. It then scales this range linearly so that it fills the entire range of possible output pixel values (ex. 0 - 255 for 8 bit data). Outlying pixel values cause a problem for this type of stretch by skewing the histogram. To compensate, the linear stretch can be given a saturation percentage. It then maps that percentage of the total pixels to both the high and low saturation points, effectively bypassing outliers, and stretches the rest of the image. The saturation percentage used by Map-a-Planet auto stretch is 0.5%.
Gaussian Like the linear stretch, this stretch finds the minimum and maximum pixel values and stretches the image between them. In the Gaussian stretch, the image is stretched to match a Gaussian, or Normal, curve. Because of the non-linear properties of the Gaussian stretch it is tolerant of outliers, but it accepts a saturation percentage to allow enhancement of median pixel values. The saturation percentage used by Map-a-Planet is 0%. Due to the analog nature of a Gaussian curve, digital representations naturally incur error. This error was placed in the spacing between the two median pixel values.
Histogram Equalization This option stretches the image so that the output has a uniform histogram. The minimum and maximum pixel values are stretched to the saturation points in the process.
Histogram Matching This option builds upon the histogram equalization. First, the image is equalized. Then, an equalized histogram of the image to be matched is consulted. The program matches the first histogram to the second. The user must supply the second equalized. Currently, the image will be matched to a Gaussian curve.
No Stretch The image will not be enhanced if "None" is chosen for the stretch.

The Image Area

Image Location and Extent

To view the latitude-longitude coordinate of a point on the image, move the mouse cursor over the image. The latitude and longitude values will be displayed below the image as illustrated in the image below.

[Latitude-longitude read-out]

Viewing geographic coordinate (highlighted text) of point on the image below the mouse cursor (hand).

At the corners of the image are displayed the minimum and maximum latitude and longitude of the displayed image. Longitude values are displayed along the top and bottom edges of the image (west on the left, east on the right). Latitude values are displayed along the left and right edges of the image (north above south).

If the image is too large to fit in the browser window, a scrollbar will appear at the bottom of the image area below the View and Save links. Use the scrollbar to view the entire image, or resize your browser window until the scrollbar disappears.

Image Mouse Navigation

The image itself can be clicked on with the mouse cursor to pan or zoom in.

[Click-and-drag to zoom]

Click, hold down the mouse button, drag to draw a box around the region to zoom in on.

[Click-and-drag zoom results]

Results of the click-and-drag zoom action. The area inside the box drawn on the image (previous image) now fills the image area.

Quick Download: View and Save

On the lower right below the image is a line titled View and Save followed by two links, described below. To download the image or World file, click the appropriate link to View the file, and select Save in your browser's File menu to save the file to your computer. Alternatively, right-click the link and select the option "Save target as" or "Save link as" (the name of this option depends on the browser).


Ordering Image Products

[Order image button]

To order (for delivery via network download) an image in a variety of image formats, click the Order button (blue shopping cart). Ordering images is completely free. You will be contacted by e-mail when your order is ready for download.

Order Settings and Information

The settings that will be used to create your image map are shown at the top of the form. A description of these settings is provided in a table in the Image Information section. To modify the settings, used the Advanced Options at the bottom of the form (click the Advanced Options title if this part of the form is hidden) or follow the link to return to your image map. See the help for Advanced Options for more about modifying the image settings.

If you'd like to choose which bands of the image to include in your order, modify the Bands entry in the Advanced Options on the order page. Type the band numbers (separate numbers with a comma) you'd like to include in your order. For example, if you'd like to include bands 1, 3, 4, and 5 of the Clementine multispectral data set, type 1,3,4,5 in the Bands entry box. For more information about the data sets, see the Map-a-Planet Data Sets page. Some image formats (described below) support only one or three bands.

Fill in your e-mail contact information. This information will be used to e-mail you with instructions when your order is ready for you to download.

Choose the Image Format by clicking the radio button next to the format you'd like. The table below briefly describes the number of bands each image format supports and provides a brief description.

Format No. Bands Color depth Description
JPEG 1 or 3 24-bit RGB color, 8-bit grayscale. Great option if you don't know which image format you want. JPEG is supported by most image software.
GIF 1 or 3 8-bit indexed color, 8-bit grayscale. Like JPEG, this format is well supported by most image software.
TIFF Multiple Multiple bands. 8-bits or 16-bits per channel. This is a great option for GIS (as well as other software applications) because TIFF supports 16-bit data (typical of topography data), multiple bands, and is well supported by GIS and image software alike.
PDS Multiple 8, 16, 32-bits per channel. PDS format is a good choice for scientific software users. PDS format retains the complete image information, including mission, instrument, geospatial parameters, and other metadata not typically present in non-scientific image formats. Some scientific software, like our Isis image processing and cartography package, supports PDS format.
ISIS Multiple. 8, 16, 32-bits per channel. The Integrated System for Imagers and Spectrometers (ISIS) is a specialized image processing package. Map-A-Planet requests for ISIS currently provide products in ISIS2 form. ISIS has many standard image processing operations such as contrast stretch, image algebra, filters, and statistical analysis. ISIS operates on both classical two-dimensional images as well as three-dimensional cubes collected from imaging spectrometers.
RAW Multiple. 8, 16, 32-bits per channel. Another well supported format by many image, GIS, and scientific applications. While not as easy to use or well supported as TIFF, RAW is very flexible.

Apply Custom Function (Equation entry - all datasets)

Users may enter custom functions to be applied to ordered datasets. These functions are simple math or algebraic equations that perform operations on requested image band(s) on a pixel by pixel basis. Function formulas need to follow a simple yet specific syntax (more below). The 'f1' variable refers to the 1st/single band entry, and for multi-band products, 'f2' refers to 2nd band, etc. A limited implementation of ISIS application 'fx' (link includes syntax information) applies the requested function to the ordered dataset. Resulting product is a single band 32bit (LSW) image file. Note the following formula examples (additional examples are described below in ".. Preset Elemental Abundance Algorithm .." section).

Use at own risk! Free form text is not error checked. All bands operated on must be present in the data selected and requested in 'Bands' field ('Advanced Options').
Function Description "Bands:"
entry *
f1*0.5 multiply first band (per entry in 'Bands' field) by 0.5 1
(f2/f1)*atan(f3/f1) multiply the ratio of band2/band1 (per entry in 'Bands' field) by the arc-tangent of band3/band1 1,2,3
f3*1000.0 multiply band3 (per entry in 'Bands' field) by 1000 1,2,3
Resulting products are single band - 32bit LSW
*Must enter successive bands to operate on final band

Apply Post-Processing Empirical Calibration to Clementine UVVIS and NIR bands

PDS has released Clementine UVVIS (Eliason et al., 1997) and NIR (Gaddis et al., 2007) image mosaics that have undergone 'full' processing and these are presented here as global maps. A final, empirical calibration step is necessary to adjust the data to improve comparison to Earth-based telescopic spectra for major lunar surface units (see Comparison_clem_usgs_Lucey.pdf). Paul Lucey and colleagues at the University of Hawaii derived empirical correction parameters to force UVVIS bands 2, 3, 4 and 5 and NIR bands 1, 2, 3, and 4 to match average spectra extracted for major geologic units in the Aristarchus plateau region of the Moon. Note that UVVIS band 1 (415 nm wavelength) was excluded because that wavelength is not present in the telescopic data; NIR bands 5 and 6 were excluded because of residual, uncorrected thermal effects in the data. For each wavelength of the bands corrected, Lucey found a gain (multiplicative) and offset (additive) correction pair that minimized these differences:

telescopic(wavelength)/telescopic(750) and [(Clem(wavelength) x gain (wavelength) + offset(wavelength)]/Clementine(750)

We recommend use of these correction factors. Unfortunately, because they are applied across dataset and PDS volume boundaries, it is simplest to provide them here separately. To order Clementine UVVIS and NIR data with these factors applied, utilize the "Apply Custom Function ..." option as described above, with the recommended correction parameters for each wavelength (in microns) as described below. For these particular corrections, each desired band is ordered as a single file (ISIS, RAW, or PDS) with the requirement that users combine ("stack") the resulting images into a multi-band file within your desired application (e.g. "cubeit" in ISIS).

Clementine
Band
Wavelength
(µ)
Gain Offset Custom
Function
"Bands:"
entry *
UVVIS 1 0.415 1.0 0.0 N/A - order as 32bit 1,2
UVVIS 2 0.750 1.0 0.0 N/A - order as 32bit
UVVIS 3 0.900 1.012 -0.0004 f3*1.012-0.0004 1,2,3
UVVIS 4 0.950 1.036 -0.0008 f4*1.036-0.0008 1,2,3,4
UVVIS 5 1.000 1.056 -0.002 f5*1.056-0.002 1,2,3,4,5
NIR 1 1.100 0.870 0.0246 f1*0.870+0.0246 1
NIR 2 1.250 0.854 0.0316 f2*0.854+0.0316 1,2
NIR 3 1.500 0.792 0.0514 f3*0.792+0.0514 1,2,3
NIR 4 2.000 0.742 0.0680 f4*0.742+0.0680 1,2,3,4
Resulting products are single band - 32bit LSW
*Must enter successive bands to operate on final band

Apply Preset Elemental Abundance Algorithm (Clem-UVVIS only)

Several algorithms are available for deriving thematic and/or elemental abundance from Clementine UVVIS data. Note the following function descriptions for each available algorithm (Bands 1-5 = f1,f2,f3,f4,f5). The ISIS application 'fx' applies these functions to the ordered UVVIS dataset. Additional information, references, and output file descriptions are available here.

FeO Lucey 2000 17.427*(-ATAN(((f4/f2)-1.19)/(f2-0.08)))-7.565
FeO Lawrence 2002 25.7*((-0.147+0.372*(-(f4/f2-1.22)/(f2-0.04))+(-0.036)*(-(f4/f2-1.22)/(f2-0.04))**2))+2.15
FeO Wilcox 2005 -137.97*((f2*0.9834)+(f4/f2*0.1813))+57.46
OMAT Lucey 2000 SQRT((f2-0.08)**2+((f4/f2)-1.19)**2)
OMAT Wilcox 2005 (f2*0.1813)-((f4/f2)*0.9834)
TiO2 Lucey 2000 3.708*(ATAN(((f1/f2)-0.42)/(f2-0.0)))**5.979

GIS World File

Choose whether or not you'd like a GIS World File generated for your images. A World file describes the location and scale of an image. Most GIS software can open and correctly display images that have an accompanying World file.

Submit Order

When the information has been completed, click the Submit Order. You will receive an e-mail within 24 hours (usually less) with instructions when your image map is ready for you to download.

Ordering Image Downloads Navigation Toolbar Data Sets Image Information Image Information Advanced Options Advanced Options Image Area Explorer Screenshot - Highlight Area and Click to View Help