IDL Reference Guide: Procedures and Functions

IMAP

The IMAP procedure creates an iTool and associated user interface (UI) configured to display and manipulate image and contour data that is georeferenced, as well as shapefile data that is interactively imported once an iMap tool is created.

This procedure is written in the IDL language. Its source code can be found in the file imap.pro in the lib/itools subdirectory of the IDL distribution.

For more information on using the iMap tool, see Working with Maps.

Syntax

Empty Map Projection

IMAP [, MAP_PROJECTION=string]

Image Visualization

IMAP [, Image[, X, Y]] [, GEOTIFF=variable] [, GRID_UNITS=value] [, MAP_PROJECTION=string]

Contour Visualization

IMAP [, Z[, X, Y]] , /CONTOUR [, GRID_UNITS=value] [, MAP_PROJECTION=string]

iTool Common Keywords: [, ANISOTROPIC_SCALE_2D=value] [, ANISOTROPIC_SCALE_3D=value] [, BACKGROUND_COLOR=value] [, DIMENSIONS=[x, y]] [, /DISABLE_SPLASH_SCREEN] [, /FIT_TO_VIEW] [, IDENTIFIER=variable] [, LOCATION=[x, y]] [, MACRO_NAMES=string or string array] [, NAME=string] [, /NO_SAVEPROMPT] [, OVERPLOT=iToolID] [, RENDERER={0 | 1}] [, SCALE_ISOTROPIC=value] [, STYLE_NAME=string] [, TITLE=string] [, VIEW_GRID=[columns, rows]] [, /VIEW_NEXT] [, VIEW_NUMBER=integer] [, VIEW_TITLE=string] [, VIEW_ZOOM=value]

iTool Image Keywords: This procedure accepts all IIMAGE keywords. For more information, see IIMAGE.

iTool Contour Keywords: If the CONTOUR keyword is set, this procedure accepts all ICONTOUR keywords. For more information, see ICONTOUR.

Map Projection Keywords: [, CENTER_LATITUDE=value] [, CENTER_LONGITUDE=value] [, DATUM=string] [, FALSE_EASTING=value] [, FALSE_NORTHING=value] [, HEIGHT=value] [, HEMISPHERE={0 | 1}] [, HOM_AZIM_LONGITUDE=value] [, HOM_AZIM_ANGLE=value] [, HOM_LATITUDE1=value] [, HOM_LATITUDE2=value] [, HOM_LONGITUDE1=value] [, HOM_LONGITUDE2=value] [, IS_ZONES=value] [, IS_JUSTIFY=value] [, LIMIT=[latmin, lonmin, latmax, lonmax]] [, MERCATOR_SCALE=value] [, OEA_ANGLE=value] [, OEA_SHAPEM=value] [, OEA_SHAPEN=value] [, SEMIMAJOR_AXIS=value] [, SEMIMINOR_AXIS=value] [, SOM_INCLINATION=value] [, SOM_LONGITUDE=value] [, SOM_PERIOD=value] [, SOM_RATIO=value] [, SOM_FLAG=value] [, SOM_LANDSAT_NUMBER=value] [, SOM_LANDSAT_PATH=value] [, SPHERE_RADIUS=value] [, STANDARD_PARALLEL=value] [, STANDARD_PAR1=value] [, STANDARD_PAR2=value] [, TRUE_SCALE_LATITUDE=value] [, ZONE=value]

Axis Keywords: [, [XY]GRIDSTYLE={0 | 1 | 2 | 3 | 4 | 5 | 6}] [, [XY]MAJOR=integer] [, [XY]MINOR=integer] [, [XY]RANGE=[min, max]] [, [XY]SUBTICKLEN=ratio] [, [XY]TEXT_COLOR=RGB vector] [, [XY]TICKFONT_INDEX={0 | 1 | 2 | 3 | 4}] [, [XY]TICKFONT_SIZE=float] [, [XY]TICKFONT_STYLE={0 | 1 | 2 | 3}] [, [XY]TICKFORMAT=string or string array] [, [XY]TICKINTERVAL=value] [, [XY]TICKLAYOUT={0 | 1 | 2}] [, [XY]TICKLEN=value] [, [XY]TICKNAME=string array] [, [XY]TICKUNITS=string] [, [XY]TICKVALUES=vector] [, [XY]TITLE=string]

Image Visualization Arguments

Image

A vector, a two-dimensional array, or a three-dimensional array representing the sample values to be displayed as an image.

If Image is a vector:

If Image is a two-dimensional array:

If Image is a three-dimensional array:

X

Either a vector or a two-dimensional array representing the x-coordinates of the image grid.

If the Image argument is a vector:

If the Image argument is a two-dimensional array (for which neither dimension is 3):

Y

Either a vector or a two-dimensional array representing the y-coordinates of the image grid.

If the Image argument is a vector:

If the Image argument is a two-dimensional array:

Contour Visualization Arguments

Z

A vector or two-dimensional array containing the values to be contoured. If the X and Y arguments are provided, the contour is plotted as a function of the (x, y) locations specified by their contents. Otherwise, the contour is generated as a function of the two-dimensional array index of each element of Z.

X

A vector or two-dimensional array specifying the x-coordinates for the contour surface. If X is a vector, each element of X specifies the x-coordinate for a column of Z (e.g., X[0] specifies the x-coordinate for Z[0, *]). If X is a two-dimensional array, each element of X specifies the x-coordinate of the corresponding point in Z (i.e., X_ij specifies the x-coordinate for Z_ij).

Y

A vector or two-dimensional array specifying the y-coordinates for the contour surface. If Y is a vector, each element of Y specifies the y-coordinate for a row of Z (e.g., Y[0] specifies the y-coordinate for Z[*,0]). If Y is a two-dimensional array, each element of Y specifies the y-coordinate of the corresponding point in Z (Y_ij specifies the y-coordinate for Z_ij).

Keywords

ANISOTROPIC_SCALE_2D

For two-dimensional anisotropic visualizations, set this keyword to a floating point value indicating the ratio of the Y dimension to the X dimension. The default is 0.7. If the dataspace and its contained visualizations are isotropic then this keyword is ignored.

ANISOTROPIC_SCALE_3D

For three-dimensional anisotropic visualizations, set this keyword to a floating point value indicating the ratio of the Z dimension to the X and Y dimensions. The default is 0.7. If the dataspace and its contained visualizations are isotropic then this keyword is ignored.

CONTOUR

Set this keyword to create a contour visualization from the supplied data. By default, the procedure creates an image visualization.

GEOTIFF

Set this keyword equal to a structure containing the GeoTIFF tags (for information on GeoTIFF tags, see the GEOTIFF keyword in the READ_TIFF function) from a GeoTIFF file. This keyword is only valid when creating an image visualization, and is ignored if the CONTOUR keyword is set.

FIT_TO_VIEW

Set this keyword to automatically scale the newly-created visualization so that it fills the current view. This keyword is ignored if VIEW_ZOOM is present.

MAP_PROJECTION

Set this keyword to a string specifying the name of an IDL GCTP map projection to use for the initial projection. If this keyword is specified, the allowed map projection keywords are available. Table 3-50 provides the projection names and the allowed keywords associated with them.

These properties are applied to the newly created dataspace, without affecting existing dataspaces. If you create an image with IMAP and use this keyword to define a map projection, IDL uses these properties to set up the image's projection. For more information, see Registering an Image.

BACKGROUND_COLOR

Set this keyword to an RGB value specifying the color to be used as the background color for the view. The default is [255, 255, 255] (white). The BACKGROUND_COLOR keyword can be used when a tool is being created or when a new visualization is being created in an existing tool with the use of the OVERPLOT, VIEW_NUMBER, or VIEW_NEXT keywords. The background color is applied to the current view. For example, if multiple views have been created with the VIEW_GRID keyword, and the VIEW_NUMBER keyword is used to create a visualization in the second view, use of the BACKGROUND_COLOR keyword would set the background color in the second view only.

DIMENSIONS

Set this keyword to a two-element vector of the form [width, height] to specify the dimensions of the drawing area of the specific tool in units specified by the UNITS keyword. If no value is provided, a default value of one half the screen size is used. The minimum width of the window correlates to the width of the menu bar. The minimum window height is 100 pixels.

DISABLE_SPLASH_SCREEN

Set this keyword to disable the iTools splash screen. By default, the first time an iTool is run, the splash screen is displayed.

GRID_UNITS

Set this keyword to an integer specifying the units for the image or contour grid. This keyword applies only when there is a map projection inserted. It has the following values:

IDENTIFIER

Set this keyword to a named variable that will contain the iToolID for the created tool. This value can then be used to reference this tool during overplotting operations or command-line-based tool management operations.

LOCATION

Set this keyword to a two-element vector of the form [x, y] to specify the location of the upper left corner of the tool relative to the display screen, in units specified by the UNITS keyword.

MACRO_NAMES

Set this keyword to a scalar string or an array of strings that specifies the names of one or more macros to run. The macro names are retrieved and the macros are run sequentially after the iTool and (if applicable) any visualizations have been created. If a macro of the specified name does not exist, IDL generates an error and the routine exits.

NAME

Set this keyword to a string that specifies the name of this visualization.

NO_SAVEPROMPT

Set this keyword to cause the iTool not to prompt the user to save changes when closing the tool. The default is to prompt the user to save changes.

OVERPLOT

Set this keyword to an iToolID to direct the graphical output of the particular tool to the tool specified by the provided iToolID.

Set this keyword to 1 to place the graphical output for the command in the current tool. If no current tool exists, a new tool is created.

RENDERER

Set this keyword to override the value specified by the IDL_GR_WIN_RENDERER (Windows) or IDL_GR_X_RENDERER (UNIX) preference for the iTool. IDL will use the specified graphics renderer when drawing objects within the iTool window. Valid values are:

If your platform does not have a native OpenGL implementation, IDL uses its own software implementation regardless of the value of this property. See Hardware vs. Software Rendering for details.

SCALE_ISOTROPIC

Set this keyword to indicate the scaling method to be used for the dataspace. Possible

values are:

STYLE_NAME

Set this keyword equal to a string that specifies the name of a user-defined or a system style. If a style of the specified name does not exist, IDL generates an error and the routine exits.

The style is applied using the following rules:

TITLE

Set this keyword to a string to specify a title for the tool. The title is displayed in the title bar of the tool.

VIEW_GRID

Set this keyword to a two-element vector of the form [columns, rows] to specify the view layout within the new tool. This keyword is only used if a new tool is being created. For example, if OVERPLOT, VIEW_NEXT, or VIEW_NUMBER are specified, then VIEW_GRID is ignored.

VIEW_NEXT

Set this keyword to change the view selection to the next view following the currently selected view before issuing any graphical commands. If the currently selected view is the last one in the layout, then VIEW_NEXT will cause the first view in the layout to become selected. This keyword is ignored if no current tool exists.

VIEW_NUMBER

Set this keyword to change the currently-selected view to the view specified by the VIEW_NUMBER before issuing any graphical commands. The view number starts at 1, and corresponds to the position of the view within the graphics container (not necessarily the position on the screen). This keyword is ignored if no current tool exists.

VIEW_TITLE

Set this keyword equal to a scalar string that will be placed in a text annotation centered horizontally in the current view, near the top. The text will be created with the properties (size, style, color, etc.) defined for text annotations in the current tool style.

VIEW_ZOOM

Set this keyword to a floating-point number giving the initial view zoom factor. For example, setting VIEW_ZOOM to 2.0 would give an initial zoom of 200%. The default is 1.0.

[XY]GRIDSTYLE

The index of the linestyle to be used for plot tickmarks and grids (i.e., when [XY]TICKLEN is set to 1.0). See LINESTYLE for a list of linestyles.

[XY]MAJOR

Set this keyword to an integer representing the number of major tick marks. The default is -1, specifying that IDL will compute the number of tickmarks. Setting MAJOR equal to zero suppresses major tickmarks entirely.

[XY]MINOR

Set this keyword to an integer representing the number of minor tick marks. The default is -1, specifying that IDL will compute the number of tickmarks. Setting MINOR equal to zero suppresses minor tickmarks entirely.

[XY]RANGE

Set this keyword to the desired data range of the axis, a two-element vector. The first element is the axis minimum, and the second is the axis maximum.

[XY]SUBTICKLEN

Set this keyword to a floating-point scale ratio specifying the length of minor tick marks relative to the length of major tick marks. The default is 0.5, specifying that the minor tick mark is one-half the length of the major tick mark.

[XY]TEXT_COLOR

Set this keyword to an RGB value specifying the color for the axis text. The default value is [0, 0, 0] (black).

[XY]TICKFONT_INDEX

Set this keyword equal to one of the following integers, which represent the type of font to be used for the axis text:

[XY]TICKFONT_SIZE

Set this keyword to a floating-point integer representing the point size of the font used for the axis text. The default is 12.0 points.

[XY]TICKFONT_STYLE

Set this keyword equal to one of the following integers, which represent the style of font to be used for the axis text:

[XY]TICKFORMAT

Set this keyword to a string, or an array of strings, in which each string represents a format string or the name of a function to be used to format the tick mark labels. If an array is provided, each string corresponds to a level of the axis. The TICKUNITS keyword determines the number of levels for an axis.

If the string begins with an open parenthesis, it is treated as a standard format string. See Format Codes.

If the string does not begin with an open parenthesis, it is interpreted as the name of a callback function to be used to generate tick mark labels. This function is defined with either three or four parameters, depending on whether TICKUNITS is specified.

If TICKUNITS are not specified:

The callback function is called with three parameters: Axis, Index, and Value, where:

If TICKUNITS are specified:

The callback function is called with four parameters: Axis, Index, Value, and Level, where:

Used with the LABEL_DATE function, this property can easily create axes with date/time labels.

[XY]TICKINTERVAL

Set this keyword to a floating-point scalar indicating the interval between major tick marks for the first axis level. The default value is computed according to the axis [XY]RANGE and the number of major tick marks ([XY]MAJOR). The value of this keyword takes precedence over the value set for the [XY]MAJOR keyword.

For example, if TICKUNITS = ['S', 'H', 'D'] and TICKINTERVAL = 30, then the interval between major ticks for the first axis level will be 30 seconds.

[XY]TICKLAYOUT

Set this keyword to an integer scalar that indicates the tick layout style to be used to draw each level of the axis.

Valid values include:

[XY]TICKLEN

Set this keyword to a floating-point value that specifies the length of each major tick mark, measured in data units. The recommended, and default, tick mark length is 0.2. IDL converts, maintains, and returns this data as double-precision floating-point.

[XY]TICKNAME

Set this keyword to a string array of up to 30 elements that controls the annotation of each tick mark.

[XY]TICKUNITS

Set this keyword to a string (or a vector of strings) indicating the units to be used for axis tick labeling. If more than one unit is provided, the axis will be drawn in multiple levels, one level per unit.

The order in which the strings appear in the vector determines the order in which the corresponding unit levels will be drawn. The first string corresponds to the first level (the level nearest to the primary axis line).

Valid unit strings include:

If any of the time units are utilized, then the tick values are interpreted as Julian date/time values.

[XY]TICKVALUES

Set this keyword to a floating-point vector of data values representing the values at each tick mark. If TICKVALUES is set to 0, the default, IDL computes the tick values based on the axis range and the number of major ticks. IDL converts, maintains, and returns this data as double-precision floating-point.

[XY]TITLE

Set this keyword to a string representing the title of the specified axis.

Map Projection Keywords:

CENTER_LATITUDE

Set this keyword to the latitude of the point on the earth's surface to be mapped to the center of the projection plane. Latitude is measured in degrees north of the equator and must be in the range -90 to +90. The default value is zero.

CENTER_LONGITUDE

Set this keyword to the longitude of the point on the earth's surface to be mapped to the center of the map projection. Longitude is measured in degrees east of the Greenwich meridian and must be in the range -360 to +360. The default value is zero.

DATUM

Set this keyword to a scalar string containing the name of the datum to use for the ellipsoid. The default value depends on the projection selected, but is either the Clarke 1866 ellipsoid or a sphere with a radius of 6370.997 kilometers.

Table 3-51 shows the datums (or spheroids) available for use with the DATUM keyword.

FALSE_EASTING

Set this keyword to the false easting value (in meters) to be added to each x-coordinate for the forward transform, or subtracted from each x coordinate for the inverse transform.

FALSE_NORTHING

Set this keyword to the false northing value (in meters) to be added to each y-coordinate for the forward transform, or subtracted from each y-coordinate for the inverse transform.

HEIGHT

Set this keyword to the height (in meters) above the earth's surface for satellite projections.

HEMISPHERE

Set this keyword equal to 1 to display the Southern hemisphere when using a UTM or Polar projection. Set this keyword equal to 0 (the default) to display the Northern hemisphere.

HOM_AZIM_LONGITUDE

Set this keyword to the longitude in degrees of the central meridian point where the azimuth occurs.

HOM_AZIM_ANGLE

Set this keyword to the azimuth angle, measured in degrees, east of a north-south line that intersects the center line. The center line is defined as the great circle path along which the Mercator cylinder touches the sphere.

HOM_LATITUDE1

Set this keyword to the latitude in degrees of the first point on the center line. The center line is defined as the great circle path along which the Mercator cylinder touches the sphere.

HOM_LATITUDE2

Set this keyword to the latitude in degrees of the second point on the center line. The center line is defined as the great circle path along which the Mercator cylinder touches the sphere.

HOM_LONGITUDE1

Set this keyword to the longitude in degrees of the first point on the center line. The center line is defined as the great circle path along which the Mercator cylinder touches the sphere.

HOM_LONGITUDE2

Set this keyword to the longitude in degrees of the second point on the center line. The center line is defined as the great circle path along which the Mercator cylinder touches the sphere.

IS_ZONES

Set this keyword to the number of longitudinal zones to include in the projection.

IS_JUSTIFY

Set this keyword to indicate what to do with rows with an odd number of columns. The following values are allowed:

LIMIT

Set this keyword to a four-element vector of the form [latmin, lonmin, latmax, lonmax] that specifies the boundaries of the region to be mapped. The points [lonmin, latmin] and [lonmax, latmax] are the longitudes and latitudes of two points diagonal from each other on the region's boundary.

MERCATOR_SCALE

Set this keyword to the scale factor at the central meridian (for the Transverse Mercator projection) or the center of the projection (for the Hotine Oblique Mercator projection). For the Transverse Mercator projection, the default scale is 0.9996.

OEA_ANGLE

Set this keyword to the Oblated Equal Area oval rotation angle in degrees.

OEA_SHAPEM

Set this keyword to the Oblated Equal Area shape parameter m. The value of OEA_SHAPEM determines the horizontal flatness of the oblong region, and is usually set to a value between one and three.

OEA_SHAPEN

Set this keyword to the Oblated Equal Area oval shape parameter n. The value of OEA_SHAPEN determines the vertical flatness of the oblong region, and is usually set to a value between one and three.

SEMIMAJOR_AXIS

Set this keyword to the length in meters of the semimajor axis of the reference ellipsoid. The default is the semimajor axis length of either the Clarke 1866 datum (6378206.4 meters) or the Sphere radius (6370997.0 meters), depending on the projection.

SEMIMINOR_AXIS

Set this keyword to the length in meters of the semiminor axis of the reference ellipsoid. The default is the semiminor axis length of either the Clarke 1866 datum (6356583.8 meters) or the Sphere radius (6370997.0 meters), depending on the projection.

SOM_INCLINATION

Set this keyword to the orbit inclination angle in degrees of the ascending node, counter-clockwise from the equator.

SOM_LONGITUDE

Set this keyword to the longitude in degrees of the ascending orbit at the equator.

SOM_PERIOD

Set this keyword to the period in minutes of the satellite revolution.

SOM_RATIO

Set this keyword to the Landsat ratio to compensate for confusion at the northern end of orbit. A typical value is 0.5201613.

SOM_FLAG

Set this keyword to the end-of-path flag for Landsat, where 0 is the start and 1 is the end.

SOM_LANDSAT_NUMBER

Set this keyword to the Landsat satellite number.

SOM_LANDSAT_PATH

Set this keyword to the Landsat path number. Use 1 for Landsat 1, 2, and 3; use 2 for Landsat 4, 5 and 6.

SPHERE_RADIUS

Set this keyword to the radius in meters of the reference sphere. The default value is 6370997.

STANDARD_PARALLEL

Set this keyword to the latitude in degrees of the standard parallel along which the scale is true.

STANDARD_PAR1

Set this keyword to the latitude in degrees of the first standard parallel along which the scale is true.

STANDARD_PAR2

Set this keyword to the latitude in degrees of the second standard parallel along which the scale is true.

TRUE_SCALE_LATITUDE

Set this keyword to the latitude in degrees of true scale.

ZONE

Set this keyword to an integer specifying the zone for the UTM projection or the State Plane projection.

IIMAGE Keywords Accepted

See IIMAGE for the description of the following keywords:

ALPHA_CHANNEL, BLUE_CHANNEL, CHANNEL, CLIP_PLANES, GREEN_CHANNEL, GRID_UNITS, HIDE, IMAGE_DIMENSIONS, IMAGE_LOCATION, INTERPOLATE, ORDER, RED_CHANNEL, RGB_TABLE, ZVALUE

ICONTOUR Keywords Accepted

See ICONTOUR for the description of the following keywords:

AM_PM, ANISOTROPY, C_COLOR, C_FILL_PATTERN, C_LABEL_INTERVAL, C_LABEL_NOGAPS, C_LABEL_OBJECTS, C_LABEL_SHOW, C_LINESTYLE, C_THICK, C_USE_LABEL_COLOR, C_USE_LABEL_ORIENTATION, C_VALUE, CLIP_PLANES, COLOR, DAYS_OF_WEEK, DEPTH_OFFSET, DOWNHILL, FILL, GRID_UNITS, HIDE, LABEL_FONT, LABEL_FORMAT, LABEL_FRMTDATA, LABEL_UNITS, MAX_VALUE, MIN_VALUE, MONTHS, N_LEVELS, PLANAR, RGB_INDICES, RGB_TABLE, SHADE_RANGE, SHADING, TICKINTERVAL, TICKLEN, USE_TEXT_ALIGNMENTS, ZVALUE

Examples

In the IDL Intelligent Tools system, data can be imported from the IDL Command Line (as described in Examples 2 and 3) or data can be imported via the File menu in the iTool window. For detailed information on importing data via the iTool file menu, refer to Data Import Methods.

Example 1

IMAP, MAP_PROJECTION='Lambert'  

This command opens a new iMap tool with the Lambert Conformal Conic projection loaded (Figure 3-59).

Figure 3-59: iMap Example — Empty Lambert Projection

Figure 3-59: iMap Example — Empty Lambert Projection

Example 2

file = FILEPATH('avhrr.png', SUBDIRECTORY=['examples','data'])  
data = READ_PNG(file, r, g, b)  
IMAP, data, LIMIT=[-90,-180,90,180], $  
   MAP_PROJECTION='Mollweide', RGB_TABLE=[[r],[g],[b]], $  
   IMAGE_TRANSPARENCY=50, GRID_UNITS=2, $  
   IMAGE_LOCATION=[-180,-90], IMAGE_DIMENSIONS=[360,180]  

This series of commands opens a new iMap tool and loads an image of the world, registered in degrees, into a Mollweide map projection (Figure 3-60).

Figure 3-60: iMap Example — World Image with Mollweide Projection

Figure 3-60: iMap Example — World Image with Mollweide Projection

Example 3

This example builds on Example 2, adding contours to the world image in the Mollweide projection.

clons = FINDGEN(360) - 179.5  
clats = FINDGEN(180) - 89.5  
cdata = SIN(clons/30) # COS(clats/30)  
IMAP, cdata, clons, clats, /CONTOUR, /OVERPLOT, $  
   RGB_TABLE=39, GRID_UNITS=2, $  
   N_LEVELS=10, C_THICK=REPLICATE(2,10)  

This series of commands plots the contour data atop Example 2's display (Figure 3-60).

Figure 3-61: iMap Example — Overplotted Contour Data in Rainbow Colors

Figure 3-61: iMap Example — Overplotted Contour Data in Rainbow Colors

Version History

  IDL Online Help (March 06, 2007)