What is the MDT file format?
.mdt is a GeoMedia Access Warehouse template file developed by Intergraph Corporation, now Hexagon Geospatial. Despite its distinct extension, an .mdt file is a standard Microsoft Access database in binary JET/ACE format - structurally identical to an .mdb file - pre-populated with the GeoMedia geospatial schema.
The file contains the blank table structure, relationships, indexes, and stored queries that define a standard GeoMedia Access Warehouse. When a user creates a new Access-based spatial database in GeoMedia, the application copies the .mdt template and populates the resulting .mdb data file with actual GIS feature geometry and attributes.
Because it is a valid Access/JET binary, an .mdt file can be opened in Microsoft Access, where the schema tables are visible - but no end-user GIS data is present in the template itself.
GeoMedia’s newer versions support modern spatial back-ends such as GeoPackage, PostGIS, and SQL Server, making Access Warehouse files a legacy data format. However, .mdt templates remain in use for organizations maintaining compatibility with older GeoMedia Access Warehouses. The format is Windows-only, reflecting its dependency on the Microsoft JET/ACE database engine.
Security & safety
RISK: LOWMDT is a Microsoft Access database template. No executable code; standard Access security concerns apply (macros or VBA in Access databases can run code, but GeoMedia .mdt templates do not contain macros). Safe to open in Access. Handle as any corporate GIS data - may contain schema or proprietary spatial data.
Format details
in a nutshell- Microsoft Diagnostic Tool log - Some Microsoft support/diagnostic utilities have historically used .mdt for machine diagnostic log files (unrelated to GeoMedia/Access).
Programs that open MDT files
Windows3 apps
Microsoft Access
Paid Open the .mdt as a database (File > Open, select All Files, choose .mdt); displays GeoMedia schema tables. Data-only use - no GIS functionality. 
GeoMedia (Hexagon Geospatial)
Paid GeoMedia uses .mdt files internally as templates; open the resulting .mdb warehouse from GeoMedia's GIS workspace. Not typically opened directly. Technical details
deep spec| Format type | Microsoft Access database template (binary JET/ACE format) |
| Developer | Intergraph Corporation (now Hexagon Geospatial) |
| Byte order | Little-endian (Windows/Intel native) |
| Encoding | Binary - Microsoft JET/ACE database engine format |
| Magic bytes | 00 01 00 00 followed by “Standard Jet DB” (identical to .mdb) |
| Encryption | Optional Access password protection (RC4 or AES); GeoMedia templates are typically unencrypted |
| Typical file size | 100 KB - 10 MB (template before GIS data population) |
| Content | Blank GeoMedia geospatial schema - tables, relationships, indexes, and stored queries |
| Purpose | Copied by GeoMedia to initialise new Access Warehouse .mdb files with the correct spatial schema |
| Supported OS | Windows |
| Interoperability | Openable in Microsoft Access (schema visible; no GIS feature data present in the template) |
| Legacy status | Superseded in newer GeoMedia by GeoPackage, PostGIS, and SQL Server back-ends |
| Database engine | Depends on Microsoft JET/ACE engine (same binary format as .mdb / .accdb) |
| Released | mid-1990s (with early GeoMedia releases) |
| Latest version | current with GeoMedia 2020/2023 product line (Hexagon) |
| Specification | www.hexagongeospatial.com |
MDT conversions
Community Q&A
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