25 March 2009
26 May 11
The MERLIN Electronic
Merlin Online Atlas
These illustrations provide a
summary of the information you can retrieve from the electronic atlas of
Maryland's Back (Coastal) Bays. They also provide guidance in the key steps
you need to navigate around in the atlas to locate and view all of this
You return to this first screen
when you click on the Home Icon.
There are four directions for exploration when you reach the main menu. A
click on the Back Bays button takes you to a SPOT satellite image of the back
bays and 27 overlay themes and their associated database information. The
Statewide Watershed Information button brings up a Landsat satellite image of
the entire state with a watershed boundaries layer and associated database
information. The Back Bays branch of the atlas has the greatest depth and the
most variety, so we'll use it as the example of how to use this atlas. Click
on the box labeled Back Bays. A great deal of geodata is being prepared for
viewing at this step. Please be patient; this may take time on a slow CD.
The toolbar in the atlas viewing window includes many useful functions. The
entire image for the initial Back Bays screen is sized to fit your view
window. This SPOT image is actually about 5000 lines by 4000 columns. The
other geodata in the atlas are also large, so the ability to zoom in and out
and reposition the view is necessary to get a detailed display of your area of
interest. Move the mouse along the toolbar, pausing over each icon to review
the ToolTip that identifies the button's function.
Click the Zoom Box icon
Position the cursor at the upper left of the detailed area of your
interest in the view
Click and hold the left mouse button as you drag the mouse down and to
the right until the box created is as wide as desired.
Click the right mouse button to zoom in on thearea of the box (on a Mac, hold
the Command key and click the mouse)
Area of box zoomed in
The Back Bays hierarchy
The Back Bays portion of the atlas has three basic levels. At the first level,
you view the SPOT image as a reference layer and turn on or off any of the
overlay themes. The second level is the same geographic area but uses 11
adjacent 7.5' USGS topographic map quadrangles as reference layers and allows
overlay of all the themes. The third level uses 36 adjacent 3.75'
color-infrared orthophoto quadrangle maps as reference layers, and again you
can overlay all the themes. (Only the SPOT image, Berlin 7.5', Berlin NE
3.75', and Ocean City NW 3.75' maps are at full resolution. The remainder of
the maps are sampled.) You can move to the next reference level at any time by
clicking the mouse at the point of interest in the current reference layer.
The position of your mouse click determines which area of the next reference
level is displayed. If you happen to click in a position where the individual
quads overlap in the next level, the HyperIndex Link Selection window opens,
and you can point and click to choose which of the overlapping quads to
You return to a previous reference level
by clicking on the Previous Level icon.
Note: if you have been viewing database tables, making measurements, or
using the Zoom Box or Slide View tool, you must switch back to the
HyperIndex tool before you can use the mouse to move through the atlas.
How to see more
The SPOT image and quad maps provide a reference framework for the many
themes, which are initially hidden. A Layer Controls window opens with each
Back Bays reference layer and lists all the information themes available for
viewing. When you choose to show a hidden layer, it is drawn on top of the
existing image. Because geodata making up this atlas is read from CD-ROM,
every layer drawn adds to display time.
Click on a layer
to select it.
The (-) mark means
the layer is hidden.
Click the Show Layer button
to turn the selected layer on/off.
Scroll to the bottom of the Layer Controls list.
Click on the 7.5' USGS quad grid outlines in the Layer Controls window
(for example, WORCGRID / QUAD_GRIDS) then on the Show Layer toggle button
Click on the State Highway Administration's Highway Mapping Team's
roads layer (for example, ROADS / ROADS_YELLOW) then on the Show Layer
7.5' map quad outlines
Clicking on the Redraw icon recomposes the viewing window, drawing all layers
chosen for viewing in correct drawing order. You need to use this icon if you
want to eliminate layers that were selected for drawing then hidden again.
Also, polygons with solid fill colors in overlay themes become lightly tinted
and transparent to the layers below when redrawn.
Choosing Locator from the View menu opens a small version of the full image
that contains an elastic box to show your current view. This box can be
repositioned and resized, and the effects are seen in the larger view window
when you click on the Apply button.
Getting more detail
Only the Berlin NE color-infrared orthophoto quarter quad has an overlay theme
with parcel maps and land ownership information. You can navigate to this
level with a few well-positioned mouse clicks.
Click on the
HyperIndex icon in the toolbar
with your view
positioned as shown in the How to see more section, place the cursor
over the creek below the cluster of roads near the upper right of the central
map grid outline (the northeast quarter of the Berlin quadrangle), and click
the left mouse button.
Berlin quad is displayed, click the left mouse button in the center of the
view to move to the next level
scroll to the
bottom of the Layer Controls window after the color- infrared orthophoto is
displayed, click on the layer containing land parcel boundaries for this area
(WORCO21 / TAXMAP_RASTER), then click on the Show Layer button; repeat for the
land parcel centroids layer (TAXCENT / CENTROIDS). (If these layers are
absent, the cursor's position was geographically incorrect for one of the
mouse clicks; either start over or consult the later section on the HyperIndex
Navigator and locate the Berlin NE digital ortho quarter quad.)
Choosing to Examine Attributes opens the Element Selection window and changes
the active tool in the view window from the HyperIndex tool to the Select
tool. Don't be intimidated by the Element Selection window. The scrolling
portion of the window is merely a repeat of the Layer Controls window with
icon buttons added. Some of these icon buttons expand the level of detail
shown. For example, you can display detailed land ownership information about
any parcel with just a few mouse clicks.
Attributes from the Examine menu.
scroll to the
bottom of the layers list in the Element Selection window
click on the
TAXCENT / CENTROIDS layer icon
click on the
Show Tables icon
click on the
view Table icon for TABLE
Record from the Table menu in the CENTROIDS / PointData / Table view
click on any
of the centroids that are in the view of the layers
The HyperIndex® Navigator
reach the map quadrangle level, the Navigator window is quite useful. It lets
you click a button and move to the nearest adjacent quadrangles or other
reference layers at the same level, such as the scanned photographs of
historic locations. If an arrow is dimmed, there is nothing in that direction.
The name of the reference layer available in the direction of any active arrow
is provided as a ToolTip. Once you click on the Show HyperIndex Navigator
icon, the window will be open whenever the HyperIndex tool is active (until
you click on the Show HyperIndex Navigator icon again to close it).
Six different tools are provided for making measurements on any view.
Snapshot printing is provided to print any view on letter size paper. Click
on the Print Snapshot icon on the toolbar. The Page Setup window may open the
first time you print if your Windows printer setup is incomplete. Printing may
be slow with your Windows print driver. The atlas contains text files you can
print to better understand the purpose and operation of the atlas. There are
also many detailed metadata files for information about the data.
If you get a blank page when printing, change your printer spooling setup
in Windows from the default to either of the other two options.
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