Chart Quilting
Chart quilting is a way to display parts of several charts together on the screen, redrawn to the same scale.
Limitation
Mercator charts, Transverse Mercator charts and Polyconic chart are quilted separately and don't mix. The transition from one form of quilting to the other is seamless. Black areas can appear in Tmerc and Polyconic quilt in areas where there is no chart cover.
By quilting, any information available in the white border around a chart, will be hidden.
To see this information hit "F9" to temporarily get into single mode display.
Skewed charts don't quilt, unless the skew is less than 5°.
Quick Start
Go to ToolBox -> Settings -> Enable Chart Quilting. Tick he box. Once quilting is on in the Toolbox, F9 becomes a toggle switch to temporarily get into single mode display. Zooming in, automatically brings up larger scale charts, if available. Panning reveals a continuous quilt of the available charts. If you started with a raster chart, only raster-charts, and perhaps CM93, will be in the quilt. The same logic applies to S57 Vector Charts (ENCS). Make sure you are familiar with the Status Bar as this will help you interpret all available information. The quilt, like a single chart can be displayed North Up or Course Up read more: Auto Follow and Display Orientation.
More details
What is the use of this feature?
In single chart mode, getting near the edge of the chart there is no information outside the chart.
OpenCPN has two modes of displaying charts, single chart mode and quilting mode.
To activate chart quilting go to Toolbox -> Settings -> Chart Display Options and tick the box "Enable Chart Quilting", tick the box "Show Chart Outlines" at the same time as this will help you see which chart mode is active. For CM93 the outline of individual charts can bee seen only if quilting is disabled.
Full Screen Quilting. Toolbox -> Settings -> Disable Fullscreen Quilting. By default all visible charts of an appropriate scale are used in the quilt. With this box checked only charts that overlap the center of the screen are used in the quilt. Checking this box is easier on the system and may give a performance boost in certain circumstances.
Is Chart quilting on?
There are some visual indications on screen to confirm if quilting is on or off.
More than one chart can be displayed and active at the same time, on the picture above, for example there are three pale blue buttons, as there are three raster-charts in this quilt. In single mode only one chart button is highlighted at a time.
Depth units that is normally shown in the upper right corner of the display, if activated in the toolbox, is only displayed in quilting mode if all participating charts uses the same unit.
Zoom level, normally displayed on the far right on the Status bar, is not present in quilting.
Many of these features are illustrated in this screen-dump.
This is a quilt consisting of three raster charts, two that are actually displayed and one smaller scale chart that is hidden behind the larger scaled charts of St Croix.
This is the button for the not displayed chart in the quilt.
The mouse pointer is over the middle raster chart and the chart information box is shown, together with the red highlighting of the chart on the screen.
No depth unit is shown in the quilt as the left chart is in Feet and the right in Fathoms an parts thereof. Notice the lack of zoom level in the status bar, a quilt , by definition, consists of several different zoom levels.
Which charts are quilted?
There are several rules built into OpenCPN governing exactly how different charts reacts to the quilting mode.
Raster charts and Vector charts are quilted separately and don't mix together. You can quilt either raster charts or vector charts, but not both at the same time.
The exception to this rule is that CM93 ver2 charts, if available, are shown if no other Mercator chart cover exists for a displayed area, for both raster- and vector- chart quilting.
Transverse Mercator Charts, which are all raster charts, are strictly quilted on their own. In this case, black areas can occur where there is no coverage.
Polyconic Charts, which are all raster charts as well, are also strictly quilted on their own. In this case, black areas can occur where there is no coverage.
CM93 ver2 charts can be quilted separately.
Mercator Charts are always quilted in quilting mode but don't quilt together with Transverse Mercator charts or Polyconic charts.
Polyconic Charts, are quilted separately, and don't mix with Mercator or Transverse Mercator Charts
Skewed Charts are allowed in the quilt as long as they don't deviate more than 5 degrees
from North Up.
Transverse Mercator Charts are quilted separately from Mercator- and Polyconic- Charts.
User control.
Users can control if an individual chart, is allowed in the quilt or not. Right clicking on any chart in a quilt and clicking "Remove this chart from quilt" on the pop up menu, removes the chart from the quilt. The chart button in the Status bar changes to
.
To activate the chart again right click this button an then click "Ad this chart to quilt"
Known issues with some NOAA ENC:s
Some NOAA ENC:s are produced with "holes" in. OpenCPNs present quilt handling is not geared to handle this, and gray areas can under some circumstances be visible. The picture above is from S:t Croix in the Caribbean. Gray areas of three different kinds are visible.
The Northern gray rectangle is an "unsurveyed" area, where, strangely enough, a smaller scale chart is available with a "survey". Use the ChartBar to switch to the smaller scale chart if necessary. Note the black frame.
The Middle two gray rectangles are "holes" in a small scale chart, where larger scale charts exists. Once again use the chart bar. Tick Toolbox->Etc "Preserve scale when changing charts" to keep the same scale when switching to larger scale charts. Note that the areas are framed in green, indicating that larger scale charts are available.
The Southern gray rectangle is a "hole" with no information available at all, and no other ENC charts are available. Note that there is no frame at all around this area.
Limitation
Mercator charts, Transverse Mercator charts and Polyconic chart are quilted separately and don't mix. The transition from one form of quilting to the other is seamless. Black areas can appear in Tmerc and Polyconic quilt in areas where there is no chart cover.
By quilting, any information available in the white border around a chart, will be hidden.
To see this information hit "F9" to temporarily get into single mode display.
Skewed charts don't quilt, unless the skew is less than 5°.
Quick Start
Go to ToolBox -> Settings -> Enable Chart Quilting. Tick he box. Once quilting is on in the Toolbox, F9 becomes a toggle switch to temporarily get into single mode display. Zooming in, automatically brings up larger scale charts, if available. Panning reveals a continuous quilt of the available charts. If you started with a raster chart, only raster-charts, and perhaps CM93, will be in the quilt. The same logic applies to S57 Vector Charts (ENCS). Make sure you are familiar with the Status Bar as this will help you interpret all available information. The quilt, like a single chart can be displayed North Up or Course Up read more: Auto Follow and Display Orientation.
More details
What is the use of this feature?
In single chart mode, getting near the edge of the chart there is no information outside the chart.
The situation changes dramatically when quilting mode is activated. The amount of relevant information on the screen increases.
Displaying charts
OpenCPN has two modes of displaying charts, single chart mode and quilting mode.To activate chart quilting go to Toolbox -> Settings -> Chart Display Options and tick the box "Enable Chart Quilting", tick the box "Show Chart Outlines" at the same time as this will help you see which chart mode is active. For CM93 the outline of individual charts can bee seen only if quilting is disabled.
Full Screen Quilting. Toolbox -> Settings -> Disable Fullscreen Quilting. By default all visible charts of an appropriate scale are used in the quilt. With this box checked only charts that overlap the center of the screen are used in the quilt. Checking this box is easier on the system and may give a performance boost in certain circumstances.
Is Chart quilting on?
There are some visual indications on screen to confirm if quilting is on or off.
- The colored rectangles in the status bar have rounded corners and the white borders of the charts are invisible when quilting is on. When quilting is off the colored rectangles has square corners.
- If you have the status bar visible at he bottom of the screen "zoom + factor" to the far right, is only shown in single mode.
- When hovering with the mouse pointer over a inactive raster chart button in single chart mode, a thumbnail of the chart is displayed in the upper left corner of the screen. At the same time an information box pops up above the button with details about the chart. This changes with quilting as the thumbnail is replaced with a high-lighting of the charts part in the quilt with a transparent reddish color.
- The exception to the last rule is CM93 charts. When an area is only covered by CM93 charts, indicated by a long yellow chart button in the status bar, and in quilting mode, no info-box is displayed and no reddish highlighting is taking place.
- When CM93 quilting is off, the outline of the individual cells are outlined in magenta.
More than one chart can be displayed and active at the same time, on the picture above, for example there are three pale blue buttons, as there are three raster-charts in this quilt. In single mode only one chart button is highlighted at a time.
Depth units that is normally shown in the upper right corner of the display, if activated in the toolbox, is only displayed in quilting mode if all participating charts uses the same unit.
Zoom level, normally displayed on the far right on the Status bar, is not present in quilting.
Many of these features are illustrated in this screen-dump.
This is a quilt consisting of three raster charts, two that are actually displayed and one smaller scale chart that is hidden behind the larger scaled charts of St Croix.
This is the button for the not displayed chart in the quilt.The mouse pointer is over the middle raster chart and the chart information box is shown, together with the red highlighting of the chart on the screen.
No depth unit is shown in the quilt as the left chart is in Feet and the right in Fathoms an parts thereof. Notice the lack of zoom level in the status bar, a quilt , by definition, consists of several different zoom levels.
Which charts are quilted?
There are several rules built into OpenCPN governing exactly how different charts reacts to the quilting mode.
Raster charts and Vector charts are quilted separately and don't mix together. You can quilt either raster charts or vector charts, but not both at the same time.
The exception to this rule is that CM93 ver2 charts, if available, are shown if no other Mercator chart cover exists for a displayed area, for both raster- and vector- chart quilting.
Transverse Mercator Charts, which are all raster charts, are strictly quilted on their own. In this case, black areas can occur where there is no coverage.
Polyconic Charts, which are all raster charts as well, are also strictly quilted on their own. In this case, black areas can occur where there is no coverage.
CM93 ver2 charts can be quilted separately.
Mercator Charts are always quilted in quilting mode but don't quilt together with Transverse Mercator charts or Polyconic charts.
Polyconic Charts, are quilted separately, and don't mix with Mercator or Transverse Mercator Charts
Skewed Charts are allowed in the quilt as long as they don't deviate more than 5 degrees
from North Up.
Transverse Mercator Charts are quilted separately from Mercator- and Polyconic- Charts.
User control.
Users can control if an individual chart, is allowed in the quilt or not. Right clicking on any chart in a quilt and clicking "Remove this chart from quilt" on the pop up menu, removes the chart from the quilt. The chart button in the Status bar changes to
.To activate the chart again right click this button an then click "Ad this chart to quilt"
Known issues with some NOAA ENC:s
Some NOAA ENC:s are produced with "holes" in. OpenCPNs present quilt handling is not geared to handle this, and gray areas can under some circumstances be visible. The picture above is from S:t Croix in the Caribbean. Gray areas of three different kinds are visible.
The Northern gray rectangle is an "unsurveyed" area, where, strangely enough, a smaller scale chart is available with a "survey". Use the ChartBar to switch to the smaller scale chart if necessary. Note the black frame.
The Middle two gray rectangles are "holes" in a small scale chart, where larger scale charts exists. Once again use the chart bar. Tick Toolbox->Etc "Preserve scale when changing charts" to keep the same scale when switching to larger scale charts. Note that the areas are framed in green, indicating that larger scale charts are available.
The Southern gray rectangle is a "hole" with no information available at all, and no other ENC charts are available. Note that there is no frame at all around this area.