Accessed in the **Contents** pane by clicking the
coordinate system picker button for the component.

The **Repair Initial Coordinate System**
command is used to correct errors in the assignment of an initial coordinate
system. Such errors usually occur in one of two ways:

The source format specified the wrong initial coordinate system.

The user manually specified the wrong initial coordinate system using the

**Assign Initial Coordinate System**dialog.

Modern formats designed to store spatial data will automatically specify
the coordinate system to be used for the data they provide. Data
from such sources will import seamlessly into Manifold with the initial
coordinate system automatically assigned. In the Contents pane the
coordinate system for the component will appear in **black**
text, indicating it has been assigned and the component is ready to go.

Sometimes there is an error in the source data. For example, if a GIS operator wrongly specifies that a drawing uses Lambert Conformal Conic projection when it uses a Transverse Mercator projection, and then saves the drawing in a format that conveys coordinate system data, the file will wrongly state to every GIS that imports that drawing that it uses Transverse Mercator. When imported into Manifold, the data will earnestly tell Manifold, with the full force and power and precision of the format, that it uses Lambert Conformal Conic and Manifold will believe it.

The drawing ends up imported into Manifold marked as having Lambert Conformal Conic as the assigned initial coordinate system. Until we try to use that drawing as a layer together with other drawings or images which are not in error, we might not notice the mistake. When we do notice the mistake we can use the Repair Initial Coordinate System dialog to change the assigned initial coordinate system to the correct Transverse Mercator coordinate system.

A more frequent use of the Repair Initial Coordinate System command
is to repair errors made with the **Assign Initial Coordinate
System** dialog. Sometimes we must import data that we
know is projected but which is stored in a format that does not specify
projection (coordinate system) information. In such cases
we might use the Assign Initial Coordinate System dialog to try a best
guess, for example Latitude / Longitude. If that does
not result in the imported drawing correctly lining up with other, "known
good" layers, we might want to try some other guesses. For
those we can use the Repair Initial Coordinate System command.

A related case is when we use Assign Initial Coordinate System to assign
the initial coordinate system and we get most, but not all, of the coordinate
system right. For example, we might try a default **favorite coordinate system**,
Latitude / Longitude, and see that everything seems to line up OK. The
default Latitude / Longitude coordinate system built into Manifold's Favorites
list uses WGS84 as the datum, but there is a vast amount of spatial data
in the world that uses other datums, such as NAD27.

The difference between the two datums is not that much, but it can be
significant, as discussed in the **Latitude
and Longitude are Not Enough** essay. If we later discover
that our imported drawing was indeed in Latitude / Longitude, but in a
form that used the NAD27 datum, we can use the Repair Initial Coordinate
System command to adjust the assigned initial coordinate system to use
the NAD27 datum.

Repairing an initial coordinate system
is easy: Click the coordinate system picker button in the **Contents pane** and under **Repair Initial Coordinate System**
unfolds a menu that allows one of three choices:

**Edit Coordinate System**- This launches the**Coordinate System**dialog to enable choosing any one of thousands of coordinate systems.

**Choose one of the listed favorites**- By default, Manifold always provides Latitude / Longitude and Pseudo Mercator as default favorites. If other coordinate systems have been added to our favorites, those also will appear in the list.

**Edit Favorites**- Launch the Favorites dialog to enable us to add a new favorite if we like. This is a convenience that allows us to right away add another coordinate system that we know we will want as a favorite.

See the **Coordinate
System** topic for details on using that dialog.

Using the Repair Initial Coordinate System dialog is similar to using
the Assign Initial Coordinate System command. For a step-by-step
illustrated example using the Assign Initial Coordinate System command,
see the **Example:
Assign Initial Coordinate System** topic.

**Synonyms** - The terms **projection**
and **coordinate
system **are used as interchangeable synonyms in Manifold. Cartographers
favor the term **projection** while
programmers seem to prefer **coordinate
system**. This documentation uses the two terms interchangeably,
with the term **projection** tending
to be used more in GIS or display contexts and the term **coordinate
system **tending to be used more when discussing programming, SQL
or standards.

Assign Initial Coordinate System

**Favorite
Base Coordinate Systems**

**Example:
Convert a 0 to 360 Degree Projection** - We often encounter data,
both images and drawings, using latitude and longitude degrees that appears
to be in Latitude / Longitude projection but which has longitude values
from 0 degrees to 360 degrees and latitude values from 0 degrees to 180
degrees, instead of the usual arrangement of -180 degrees to 180 degrees
for longitude centered on the Prime Meridian, and -90 degrees to 90 degrees
for latitude centered on the Equator. This example shows how to
utilize such data by assigning the correct projection.

**Example:
Assign Initial Coordinate System - **Use the **Contents pane** to manually assign
an initial **coordinate
system** when importing from a format that does not specify the
coordinate system.

**Example:
Change Projection of an Image** - Use the **Change Coordinate System**
command to change the projection of an image, raster data showing terrain
elevations in a region of Florida, from Latitude / Longitude to Orthographic
centered on Florida.

**Example:
Adding a Favorite Coordinate System** - Step by step example
showing how to add a frequently used coordinate system to the Favorites
system.

**Example:
Detecting and Correcting a Wrong Projection** - A lengthy example
exploring projection dialogs and a classic projection problem. We
save a drawing into projected shapefiles and then show on import how a
projection can be quickly and easily checked and corrected if it is wrong.

**Re-Projection
Creates a New Image** - Why changing the projection of an image
creates a new image.