Some 3,000 Central American migrants prepared to cross into Mexico from Guatemala on Friday with hopes of eventually arriving to the United States. Busloads of Mexican federal police were gathering in Ciudad Hidalgo and a Mexican military helicopter flew along the river in anticipation.

Here is a look at the differences between the Guatemala-Mexico border and the U.S.-Mexico border between Tijuana and San Diego where members of a migrant caravan arrived last spring.

WHAT'S THE GUATEMALA-MEXICO BORDER LIKE?

FILE - In this April 10, 2000, file photo, a marker embedded in the pavement marks the border between the United States and Mexico at the San Ysidro border checkpoint between San Diego, Calif., and Tijuana, Mexico. The Tijuana and San Diego border crossing is the world's busiest land border crossing, but also now sees relatively few illegal crossings. (AP PhotoDamian Dovarganes, File)

FILE - In this April 10, 2000, file photo, a marker embedded in the pavement marks the border between the United States and Mexico at the San Ysidro border checkpoint between San Diego, Calif., and Tijuana, Mexico. The Tijuana and San Diego border crossing is the world's busiest land border crossing, but also now sees relatively few illegal crossings. (AP PhotoDamian Dovarganes, File)

The official border crossing is a bridge connecting the cities of Tecun Uman, Guatemala and Ciudad Hidalgo, Mexico. A gate onto the bridge on the Guatemalan side was closed Friday and blocked by police. But rafts also cross the swift-moving Suchiate River, moving cargo and people between the two countries day and night, typically without much government interference. Locals said they had been warned by Mexican authorities not to carry people. At times Mexico has stepped up its immigration patrols along the border, but it has had more success patrolling the roads leading away from the crossing where migrants catch rides or walk along the roadside.

WHAT'S THE U.S.-MEXICO BORDER LIKE?

The U.S.-Mexico border between Tijuana and San Diego is the world's busiest land border crossing. It is also the most heavily fortified segment between both countries and now sees comparatively few illegal crossings. In some places in the area, the U.S. has installed three layers of walls and fencing. There is also bright lighting, roads patrolled by the Border Patrol and surveillance technology.

FILE - In this June 22, 2016 file photo, Border Patrol agent Eduardo Olmos walks near the secondary fence separating Tijuana, Mexico, background, and San Diego in San Diego. The Tijuana and San Diego border crossing is the world's busiest land border crossing, but also now sees relatively few illegal crossings. (AP PhotoGregory Bull, File)

FILE - In this June 22, 2016 file photo, Border Patrol agent Eduardo Olmos walks near the secondary fence separating Tijuana, Mexico, background, and San Diego in San Diego. The Tijuana and San Diego border crossing is the world's busiest land border crossing, but also now sees relatively few illegal crossings. (AP PhotoGregory Bull, File)