File - Import

The File - Import command launches the  Import dialog, very similar to the standard Windows File - Open dialog, which allows browsing the Windows file system to locate and to choose the file to be imported.   The  Import dialog allows importing of file-based data sources such as files, file databases, scripts and text comments.  




In addition to the usual Windows File - Open style controls the Link dialog provides these controls:


File name - Enter the name of the file to be imported, or populate the box by clicking on a file in the display pane.  The pull-down list for the box provides a list of recently-opened files.


(File types) - Use All Files (*.*) by default or choose a specific file type to filter the types of files shown in the display pane.   For example, choosing JS Files (*.js) will only show files with a .js extension, that is, JScript script files.


Options - For many file types provides access to Cache Data option, to create and utilize an accessory .MAPCACHE file for improved performance. The Cache Data  option is checked by default.  The Cache Data  options has two options, both checked by default, one to cache only data that is expensive to dynamically compute and the other to save cached data between sessions.   It only makes sense to uncheck either option if we are desperately low on free disk space.  Note that although these options may appear as part of the Link dialog for all file types a .MAPCACHE file is not created or used with file types such as .js for JScript scripts or other file types not supporting use of .MAPCACHE.

Automatic detection of file type

The Import dialog by default browses the Windows file system using a setting of All Files (*.*) to display all files in folder regardless of the file type as specified by a three letter extension.   We can click on whatever file is of interest and the system will automatically utilize the correct dataport for that file type.   


This works remarkably well even in cases where different formats use the same three letter extension, or when no three letter extension is used.   For example, clicking on an .img file for importing will automatically cause the right dataport to be used whether that .img file is in ENVI, ERDAS, IDRISI or IMDISP .img format.   Likewise, clicking on a file with no extension will autodetect if it is a GIRAS, GLOBE or GRASS format file and will automatically use the correct dataport for import.


At times despite the system's best efforts we might have to manually specify a particular file type by choosing it from the list, but usually the automatic choice works best.



The system will automatically read projection (coordinate system) information from all formats that provide such information.   Some formats, however do not provide projection information or, like shapefiles, may or may not provide projection information.    When components are

64-bit Windows Limits on 64-bit Manifold

Due to a lack of required Microsoft facilities in 64-bit Windows systems, in most such systems Manifold in 64-bit mode cannot export, import or link to DB, HTML, MDB, XLS or WKx format files.


The workaround for importing or exporting such files is to utilize the 32-bit version of Manifold that is automatically installed in every 64-bit Manifold installation in addition to the 64-bit version of Manifold.   To import  we launch Manifold in 32-bit mode and import into a Manifold .map project file.   We can then launch Manifold in 64-bit mode and open that .map project file or link to that .map project file.  To export, we launch Manifold in 32-bit mode, open the .map project desired and export to the desired format.


For important information and discussion please see the Essay on .mdb files and 32-bit or 64-bit Manifold.


Some formats from which we might want to import files, such as Access MDB, may allow the use of passwords to control access to the file.  In such cases instead of using File - Import we should connect to the file using OLE DB (for MDB files) or other data source connection option available in File - Create - New Data Source where the dialog allows us to specify a password.


Importing Data from Sources other than Files - Sometimes we would like to import data into a project from a source other than a file-based source.   For example, we might like to import a table from a DBMS server such as an Oracle server.   We can do that by creating a new data source using the File - Create - New Data Source command, expanding the data source and then using Copy and Paste to copy the desired table and to paste it into our project.


The New Data Source dialog allows us to connect to file-based data sources as well but in addition also allows connection database servers like PostgreSQL or Oracle, generic DBMS connection technologies such as ADONET, OLEDB and ODBC and also to web servers of various kinds.    While Copy and Paste is a good approach to make local copies of tables stored on external DBMS servers it is not usually a realistic approach to attempting to make a copy of the almost limitless data stored in servers such as Virtual Earth or Google Earth.


For example, if we create a data source that is a Virtual Earth satellite image when we open that image and zoom in and pan the remote web server will send us the tiles we need to see content in the current zoom / pan viewport we are using.   But if we Copy the image's table in the data source and then Paste it as a table in our local project hierarchy, we are commanding Manifold to grab all tiles for the entire, worldwide extent of satellite imagery content in Virtual Earth.  Even if we had the hundreds of terabytes of disk space required it would take a very long time to fetch so much data via whatever Internet connection we likely have.


A big part of the idea of linking data from web servers like Virtual Earth is to avoid having local copies.   But if we do want to capture tiles for whatever views we are using we can use specialized tools other than Copy and Paste to do so.


Three Letter Extensions - Most file names in Windows end in what is called a three letter extension, which is usually three letters at the end of the file name following a dot . character.    The three letter extension is one way Windows at times (but not always) keeps track of what a file is supposed to be.    Unfortunately, by default Windows hides the three letter extensions of files and instead tries to associate files with whatever program it thinks should be used to open that file.   This is confusing when working with the many file formats that Manifold and similar products utilize.  


Therefore, please turn off the hiding of extensions by Windows.  A typical way to do so in most versions of Windows would be from Windows Explorer, choose Tools - Folder options, press the View tab and then in the Advanced Settings pane ensure that the Hide extensions for known file types is unchecked.  Press Apply to Folders and then press OK.  You will then be able to see extensions such as .map and others.  See also the Essay on three letter extensions and why the default hiding of them by Windows is such a bad thing.


See Also

File - Export


Change Projection


Initial Projection


Formats and Data Sources


SHP, Shapefiles


Latitude and Longitude are Not Enough


Shapefiles Strangely Out of Shape


MDB Files in 64-bit Windows


Three Letter Extensions


That YX Thing