A method for assembling disposable absorbent articles, each absorbent article comprising a topsheet, a backsheet, and a substantially cellulose free absorbent core disposed between the topsheet and the backsheet, the method comprising the steps of: advancing a first continuous substrate in a machine direction, the first continuous substrate having a first surface and an opposing second surface, and defining a width in a cross direction; depositing absorbent particulate polymer material on the first surface of the first continuous substrate so as to define first regions of absorbent particulate polymer material surrounding second regions that are substantially free of absorbent particulate polymer material; advancing a second continuous substrate in the machine direction, the second continuous substrate having a first surface and an opposing second surface, and defining a width in the cross direction; depositing absorbent particulate polymer material on the first surface of the second continuous substrate so as to define first regions of absorbent particulate polymer material surrounding second regions that are substantially free of absorbent particulate polymer material; combining the first continuous substrate with the second continuous substrate to create a continuous length of substantially cellulose free absorbent cores, wherein the second regions on the first continuous substrate and the second continuous substrate are placed in facing relationships to define channel regions having a first thickness T1 surrounded by absorbent particulate polymer material areas having a second thickness T2, wherein first thickness T1 is less than the second thickness T2; advancing the continuous length of substantially cellulose free absorbent cores past a sensor such that the second continuous substrate is between the sensor and the first continuous substrate; illuminating the second surface of the second continuous substrate of the continuous length of substantially cellulose free absorbent cores with a predetermined pattern of light extending in the cross direction; sensing distortions in patterns of light reflected from the second surface of the second continuous substrate with the sensor to triangulate changes in elevation of the second surface of the second continuous substrate relative to the sensor; and creating a profile representing a surface topography of channel regions in the continuous length of substantially cellulose free absorbent cores from the triangulated changes in elevation. advancing a first continuous substrate in a machine direction, the first continuous substrate having a first surface and an opposing second surface, and defining a width in a cross direction; depositing absorbent particulate polymer material on the first surface of the first continuous substrate so as to define first regions of absorbent particulate polymer material surrounding second regions that are substantially free of absorbent particulate polymer material; advancing a second continuous substrate in the machine direction, the second continuous substrate having a first surface and an opposing second surface, and defining a width in the cross direction; depositing absorbent particulate polymer material on the first surface of the second continuous substrate so as to define first regions of absorbent particulate polymer material surrounding second regions that are substantially free of absorbent particulate polymer material; combining the first continuous substrate with the second continuous substrate to create a continuous length of substantially cellulose free absorbent cores, wherein the second regions on the first continuous substrate and the second continuous substrate are placed in facing relationships to define channel regions having a first thickness T1 surrounded by absorbent particulate polymer material areas having a second thickness T2, wherein first thickness T1 is less than the second thickness T2; advancing the continuous length of substantially cellulose free absorbent cores past a sensor such that the second continuous substrate is between the sensor and the first continuous substrate; illuminating the second surface of the second continuous substrate of the continuous length of substantially cellulose free absorbent cores with a predetermined pattern of light extending in the cross direction; sensing distortions in patterns of light reflected from the second surface of the second continuous substrate with the sensor to triangulate changes in elevation of the second surface of the second continuous substrate relative to the sensor; and creating a profile representing a surface topography of channel regions in the continuous length of substantially cellulose free absorbent cores from the triangulated changes in elevation.