diff --git a/NAMESPACE b/NAMESPACE
index 2df1349..28c090e 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -4,8 +4,8 @@ S3method(ext_matrix,SpatExtent)
 S3method(ext_matrix,SpatRaster)
 S3method(ext_matrix,SpatVector)
 S3method(ext_matrix,default)
+S3method(ext_matrix,double)
 S3method(ext_matrix,matrix)
-S3method(ext_matrix,vector)
 export(calculate_travel_time)
 export(ext_from_terra)
 export(ext_matrix)
diff --git a/R/ext_matrix.R b/R/ext_matrix.R
index cbc4e44..5ff4e3a 100644
--- a/R/ext_matrix.R
+++ b/R/ext_matrix.R
@@ -1,43 +1,41 @@
 #' @title Convert extent to matrix
 #'
 #' @description
-#' This function converts from formats ...
-#' TODO - explain why we need to do this, which is that we need a special esoteric format
+#' This function allows `get_friction_surface()` to accept the argument `extent` as a `vector`, 2x2 `matrix`, `SpatVector`, or `SpatRaster` and extracts and converts into the annoyingly specific format necessary to download the friction surface. See details in `?get_friction_surface`
 #'
-#' @param x `numeric` length 4, consisting of `c(xmin, xmax, ymin, ymax)`
-#' dimensions of extent
+#' @param extent `vector` of length 4, 2x2 `matrix`, `SpatVector`, or `SpatRaster`
 #'
-#' @return 2x2 `matrix` - explain esoteric format of matrix
+#' @return 2x2 `matrix` with column names "x" and "y" and row names "min"
+#'  and "max
 #'
 #' @examples
 #' ext_matrix(c(111,112,0, 1))
-#' # TODO
-#' # add examples of all SpatRaster, SpatVector, etc.
+#'
 #' @export
-ext_matrix <- function(x, ...){
+ext_matrix <- function(extent){
   UseMethod("ext_matrix")
 }
 
 #' @export
-ext_matrix.SpatExtent <- function(x, ...){
-  extent <- ext_vect_to_matrix(x)
+ext_matrix.SpatExtent <- function(extent){
+  extent <- ext_vect_to_matrix(extent)
   extent
 }
 
 #' @export
-ext_matrix.SpatRaster <- function(x, ...){
-  extent <- ext_from_terra(x)
+ext_matrix.SpatRaster <- function(extent){
+  extent <- ext_from_terra(extent)
   extent
 }
 
 #' @export
-ext_matrix.SpatVector <- function(x, ...){
-  extent <- ext_from_terra(x)
+ext_matrix.SpatVector <- function(extent){
+  extent <- ext_from_terra(extent)
   extent
 }
 
 #' @export
-ext_matrix.vector <- function(x){
+ext_matrix.double <- function(extent){
   if (length(extent) != 4){
     cli::cli_abort(
       message = c(
@@ -46,33 +44,32 @@ ext_matrix.vector <- function(x){
         )
     )
   }
-  extent <- ext_vect_to_matrix(x)
+  extent <- ext_vect_to_matrix(extent)
   extent
 }
 
 #' @export
-ext_matrix.matrix <- function(x, ...){
-  is_2x2 <- identical(dim(x), c(2L,2L))
+ext_matrix.matrix <- function(extent){
+  is_2x2 <- identical(dim(extent), c(2L,2L))
   if(!is_2x2){
     cli::cli_abort(
       message = c(
-        "If {.arg x} is of class, {.cls matrix}, it must have dimensions: 2x2",
+        "If {.arg extent} is of class, {.cls matrix}, it must have dimensions: 2x2",
         "However, we see that {.arg x} has dimensions: \\
-        {.val {paste0(dim(x), collapse = 'x')}}."
+        {.val {paste0(dim(extent), collapse = 'x')}}."
         )
     )
   }
-  extent <- x
   extent
 }
 
 #' @export
-ext_matrix.default <- function(x, ...){
+ext_matrix.default <- function(extent){
   cli::cli_abort(
     message = c(
       "{.arg extent} must be of class {.cls numeric, matrix, \\
-      SpatExtent, SpatRaster}",
-      "But we see class: {.cls {class(x)}."
+      SpatExtent, SpatRaster, SpatVector}",
+      "But we see class: {.cls {class(extent)}}."
       )
   )
 }
diff --git a/man/ext_matrix.Rd b/man/ext_matrix.Rd
index 41f3887..0331c9e 100644
--- a/man/ext_matrix.Rd
+++ b/man/ext_matrix.Rd
@@ -4,21 +4,19 @@
 \alias{ext_matrix}
 \title{Convert extent to matrix}
 \usage{
-ext_matrix(x, ...)
+ext_matrix(extent)
 }
 \arguments{
-\item{x}{\code{numeric} length 4, consisting of \code{c(xmin, xmax, ymin, ymax)}
-dimensions of extent}
+\item{extent}{\code{vector} of length 4, 2x2 \code{matrix}, \code{SpatVector}, or \code{SpatRaster}}
 }
 \value{
-2x2 \code{matrix} - explain esoteric format of matrix
+2x2 \code{matrix} with column names "x" and "y" and row names "min"
+and "max
 }
 \description{
-This function converts from formats ...
-TODO - explain why we need to do this, which is that we need a special esoteric format
+This function allows \code{get_friction_surface()} to accept the argument \code{extent} as a \code{vector}, 2x2 \code{matrix}, \code{SpatVector}, or \code{SpatRaster} and extracts and converts into the annoyingly specific format necessary to download the friction surface. See details in \code{?get_friction_surface}
 }
 \examples{
 ext_matrix(c(111,112,0, 1))
-# TODO
-# add examples of all SpatRaster, SpatVector, etc.
+
 }
diff --git a/man/traveltime-package.Rd b/man/traveltime-package.Rd
index 90c350a..8e63b63 100644
--- a/man/traveltime-package.Rd
+++ b/man/traveltime-package.Rd
@@ -26,7 +26,7 @@ Authors:
 
 Other contributors:
 \itemize{
-  \item Nicholas Tierney (\href{https://orcid.org/0000-0000-0000-0000}{ORCID}) [contributor]
+  \item Nicholas Tierney \email{nicholas.tierney@gmail.com} (\href{https://orcid.org/0000-0003-1460-8722}{ORCID}) [contributor]
 }
 
 }
diff --git a/traveltime.Rproj b/traveltime.Rproj
index 497f8bf..2f92160 100644
--- a/traveltime.Rproj
+++ b/traveltime.Rproj
@@ -1,4 +1,5 @@
 Version: 1.0
+ProjectId: d7cb03ec-3557-4217-8f1a-4913ea040d41
 
 RestoreWorkspace: Default
 SaveWorkspace: Default