1. Introduction
The Department of Posts has undertaken an initiative to establish a Digital Public Infrastructure (DPI) for a standardized, geo-coded addressing system in India. As part of this initiative, the Department is releasing the final version of DIGIPIN – the foundation layer of the DPI. This initiative seeks to provide simplified addressing solutions for seamless delivery of public and private services and to enable "Address as a Service" (AaaS) across the country.
DIGIPIN is an open-source national-level addressing grid developed by the Department of Posts in collaboration with IIT Hyderabad and NRSC, ISRO, and is a key component of the digital address ecosystem. The beta version of the technical document on DIGIPIN was placed for public comments and expert opinion.
After thorough analysis of the comments received through various stakeholder consultations, the Department has now finalized the DIGIPIN Grid that incorporates the relevant inputs. The DIGIPIN layer will serve as a uniform address referencing framework available both offline and online, enabling logical and precise location identification with directional attributes across India, offering significant advantages of ensuring precise geographic identification and thus complementing the conventional addressing system by providing an additional attribute. This would bridge the gap between physical locations and their digital representation.
2. Design Approach
2.1 Core Concept
The DIGIPIN layer is the cornerstone of the entire digital address ecosystem. DIGIPIN is visualized as an alphanumeric offline grid system that divides the geographical territory of India into uniform 4-meter by 4-meter (approx.) units. Each of these 4m X 4m units (approx.) is assigned a unique 10-digit alphanumeric code, derived from the latitude and longitude coordinates of the unit. This alphanumeric code serves as the offline addressing reference for any specific location within the DIGIPIN system.
2.2 DIGIPIN Layer
The DIGIPIN layer will act as the addressing reference system, which will be available offline and can be used for locating addresses logically with directional properties built into it due to the logical naming pattern followed in its construction. The DIGIPIN Grid system, being an addressing referencing system, can be used as the base stack for developing other ecosystems where addressing is one of the processes in the workflow.
3. DIGIPIN: Code Architecture
The detailed structure is such that the DIGIPIN is essentially an encoding of the latitude and longitude of the address into a sequence of alphanumeric symbols using the following 16 symbols: 2, 3, 4, 5, 6, 7, 8, 9, C, J, K, L, M, P, F, T.
The process of identifying the cells is done in a hierarchical fashion. The encoding is performed at various levels, and the basic idea is the following:
- A bounding box is used that covers the entire country.
- The bounding box is split into 16 (i.e., 4x4) regions. Each region is labeled by one of the symbols 2, 3, 4, 5, 6, 7, 8, 9, C, F, J, K, L, M, P, T. The first character in the code would identify one of these regions. This is called the level-1 partition.
- Each region is then subdivided into 16 subregions in a similar fashion. Each of the 16 subregions is labeled by the 16 characters. For a given region, the subregion is identified by the second character of the code. Therefore, the first two characters of the code uniquely identify one of the 16^2=256 subregions. This is called the level-2 partition.
3.1 Bounding Box
Figure 1: DIGIPIN level-1 grid lines (yellow) overlaid over the Indian region showing the extent of the DIGIPIN bounding box
- Longitude: 63.5 – 99.5 degrees east
- Latitude: 2.5 – 38.5 degrees north
4. Key Differences Between Beta Version and Final Version of DIGIPIN
- A modification in the extent of the DIGIPIN bounding box.
- The replacement of characters G, W, and X with C, F, and T to maintain the phonetic and visual clarity of DIGIPIN.
- A uniform gridding and labeling scheme across all iterations (1-10).
5. Illustration of DIGIPIN Generation Process
The figure below illustrates the complete procedure for generating DIGIPIN for a specific location. For example, the geographical coordinates of Dak Bhawan (28.622788°N, 77.213033°E) are marked with a red star on the India base map. The figure demonstrates the selection of DIGIPIN symbols at each level based on the grid encompassing Dak Bhawan. The DIGIPIN of Dak Bhawan is 39J 49L L8T4.
| Level-1 | Level-2 |
|---|---|
 |
 |
| 3 | 9 |
| Level-3 | Level-4 |
|---|---|
 |
 |
| J | 4 |
| Level-5 | Level-6 |
|---|---|
 |
 |
| 9 | L |
| Level-7 | Level-8 |
|---|---|
 |
 |
| L | 8 |
| Level-9 | Level-10 |
|---|---|
 |
 |
| T | 4 |
Figure 4: Illustration of the procedure for deriving DIGIPIN of a known location