Mobile GIS Helped El Salvador Complete a National Census in Two Months

For over a decade, El Salvador’s true population remained a mystery, leading to policies and decisions based on outdated figures. A combination of governmental instability and limited resources contributed to a 17-year lapse in nationwide census-taking in the country. In 2024, that all changed.

Population censuses are one of the primary sources of data for implementing policies aimed at inclusive socioeconomic development and sustainability.

A new census would not only establish an accurate count of residents but also provide insights into their living conditions and most important needs. Up-to-date information about the population would inform laws and policies that affect Salvadorans’ livelihoods and well-being. Businesses could better assess growth opportunities or new markets. And the government could estimate future population growth and make data-driven decisions for the country.

First, the country needed to address challenges in capacity, funding, and support to ensure a successful census. It became clear that the Banco Central Reserve (BCR) of El Salvador could provide the needed resources to see the project through to success. In 2022, it established the Oficina Nacional de Estadística y Censos (ONEC) to merge with the General Directorate of Statistics and Census of El Salvador (Dygestic) with the objective of modernizing the data generation system. $80 million was earmarked for the project. 

The goal was to conduct a count that was 100 percent digital, with thousands of enumerators collecting data in person using mobile devices. This was part of the government’s desire to update data collection methods, reducing data errors and costs due to outdated methods of paper-and-pencil interviewing (PAPI) and creating greater efficiency.

El Salvador’s population spans dense urban areas as well as rural communities shaped by volcanic mountain regions and a low‑lying coastal plateau. Census teams needed to collect consistent, location‑accurate data across places with very different terrain, access, and field conditions. It was a multidimensional challenge—one that demanded an approach capable of adapting to many realities at once.

To conduct a completely digital census, ONEC needed a robust and user-friendly mobile solution that included surveys to capture all essential census information, with an emphasis on location. The agency also needed administrative and quality control components to ensure the accurate and timely collection of field data.

Geosis, S.A., an El Salvador-based geospatial consulting company and Esri distributor, developed the census solution that included digital surveys using Esri’s Survey123 software.
 

“When we say the census would be completely digital, we mean that enumerators were going to go building by building throughout the country to collect information. No one filled out a form ahead of time at home or in an office,” explained Geosis managing director Rolando Magaña.

Since the surveys were deployed on mobile devices to hundreds of newly trained workers, ease of use and flexibility were essential features, as well as the ability to access the surveys and maps both online and offline. Incorporating these features helped speed up the data collection process and allowed census takers to keep moving along their assigned routes.
 

“Mobile workers counted every structure and every person, as well as capturing data about types of structures and any business or agricultural activities on the premises,” continued Magaña. “If a building didn’t match its description on the map, a worker could easily report that information on the spot, as well as any other observations.”

At ONEC, an office solution in ArcGIS Pro supported between 150 and 200 workers. This included editors who made updates or corrections to data and supervisors who managed posting and addressing problems. A central hub site, built with ArcGIS Hub, was updated twice daily. This ensured timely executive oversight of the operations and allowed for quick adjustments to work plans when necessary.
 

The official 2024 census was launched on May 2, 2024, just two months after the country’s initial pilot census project ended. In the field, the workflow supported around 2,000 workers, including mobile staff and editors using ArcGIS Pro. Field operations were organized around planning, support, and quality control. The Geosis team configured multiple surveys to streamline workflows and make them clear and straightforward, adding unique icons for each survey for at-a-glance recognition.

The in-person interviews allowed enumerators to briefly explain the process to residents, overcome objections, and make on-the-spot observations about any discrepancies with previous data. They could also emphasize the importance of participating in the census and ensure that the information being collected was correct as reported to them. Careful work in the field helped reduce the risk of human error in data entry and allowed for real-time data validation.
 

Census workers could skip questions that were not relevant (such as the names and ages of children if a family had no children living with them). If no one was home when the enumerator visited, they could ask neighbors about who lived in the house and cite the neighbor’s name as the source of the information. 

Once the census worker marked their assigned area as complete and submitted that information to their supervisor, they would receive directions for the next area to be surveyed. Those instructions worked with standard mobile applications to create maps for workers to follow.

The census ended on June 26, 2024, a remarkable feat for a country with a last known population of 5.7 million. In just under two months, El Salvador completed what the US Census Bureau has called “typically the largest peacetime operation governments conduct.”

So, how many people live in El Salvador now? According to the 2024 census, 6.3 million.
 

Residents and policymakers alike can be assured that accurate data is driving critical decisions to improve the lives of all Salvadorans.