## 3 Considering the ALS Workflow and Its Impact on the Efficacy of Data Products  
To further explain the issue of raster resolution, detection limits and their relation to the sampling density (shot density) or percentage of illuminated surface let us consider Figure 10. This figure is based on data collected for the Mayapan, Yucatan project (see Table 1). The figure panels are shaded relief maps of the same area at different raster resolutions and are based on a different number of laser returns. The figure is arranged in such a way that the adjacent panels in a row will have either the same raster resolution, or if they have different resolutions the DSMs will have been generated from the same number of laser returns. For instance in the top row the shaded relief maps in the left and center panels were generated from the same ALS return dataset at different grid resolutions. However, the images at the center and right have the same raster resolution, but the DSM to the right was generated with a higher number of laser returns.  
Figure 10: Comparative illustration of the relationship between point cloud return density and raster resolution. **(a)** 1-m DSM from 5.4 returns/m\({}^{2}\); **(b)** 0.5-m DSM from 5.4 returns/m\({}^{2}\); **(c)** 0.5-m DSM from 10.9 returns/m\({}^{2}\); **(d)** 0.5-m DSM from 20.4 returns/m\({}^{2}\); **(e)** 0.25-m DSM from 20.4 returns/m\({}^{2}\); **(f)** 0.25-m DSM from 43. returns/m\({}^{2}\).  
It is obvious that a higher raster resolution will produce sharper looking images, however the amount of detail evident in the images is highly affected by the number of returns (surface samples) from which the raster is interpolated. This is very evident with the round columns that surround the main pyramid and the temple with the round \"Caracol\" structure (identified with red arrows on the bottom right image panel). The number and definition of the columns is higher in the raster that is interpolated from a higher number of returns even when the raster resolution might be the same. The summarized conclusion from this figure is that you can create an elevation raster at whatever resolution you want, but that does not mean that the raster is an accurate representation of reality unless it has enough LiDAR returns to support it, and conversely if you do not create a raster at a fine enough resolution you might miss some of the information contained in the LiDAR returns.  
Defining the raster resolution and laser shot densities that will enable the archaeologists to answer the desired research question is perhaps the most critical decision when considering LiDAR data collection for a project. This is also the first input to the mission planning process; a process the researcher should engage in as much as possible to ensure the final data products will be useful to answer the proposed research question--which is very different from ordering standardized satellite imagery. For the first archaeological ALS projects defining what kind of laser shot densities were appropriate was similar to the question of what came first, the chicken or the egg? However, by now there have been many projects that provide some reference to what can be achieved with different laser shot densities and raster resolutions for a variety of canopy covers. Data presented in Tables 1 and 2 along with the multiple figures throughout this paper provide some laser shot densities values for a baseline reference.