Modesto Calibration Baseline Rehabilitation Project

Land Surveyors can use a set of surveyed monuments located along a baseline to check the electronic distance meters on their measuring equipment. (Electronic distance meters are typically included on total station instruments, which measure both angles and distances). These monuments are certified by the National Geodetic Survey (NGS) and are known as “calibration baselines”.

There is an existing calibration baseline in Modesto, California. The Central Valley Chapter of the California Land Surveyors Association has completed the rehabilitation this calibration baseline, which fell into disuse.

The initial site inspection was completed in the Spring of 2010. The measurement of the baseline by volunteers from the CLSA California Central Valley Chapter with the assistance of NGS was completed in the Summer of 2010.

Project Updates

• Baseline Measurement Complete: The official publication of the baseline monument distances is complete. You will find the published data for our Modesto baseline in the NGS datasheet listing data for all California baselines. The data for just the Modesto baseline is also listed in the PDF linked to in the NGS Results section below.
• Baseline Measurement Complete: The measurement of the baseline monuments was completed by CLSA Central Valley Chapter volunteers and NGS. The baseline measurement took two (2) long days of field work. Staff from the City of Manteca, City of Modesto, Stanislaus County, Northstar Engineer, and KSN spent portions or all of the two (2) days assisting at the baselines. (The chapter sent letters of appreciation and thanks to each organization that contributed trucks, equipment, and man hours to the baseline measurement.) You can view photos of the baseline measurement below.
• Site Inspection Complete: Keith Spencer and Landon Blake performed a site inspection at the CBL site in Modesto. They recovered and took photographs of all four (4) CBL monuments. The photographs, written description of the monument locations, and monument coordinates provided by the Stanislaus County Surveyor Department were all delivered to Marti Ikehara, the NGS Advisor for California.
• CBL Measurement Date Scheduled: Monday, August 23 and Tuesday, August 24 are the dates tentatively schedule for measurement of the CBL monuments with the equipment from NGS. This means leveling work at the baseline will need to be performed at the end of June or beginning of August.

Site Inspection Data

You can download the photos, written descriptions, and approximate monument coordinates for the Modesto Baseline.

NGS Results

You can download the Calibration Results for the Modesto Baseline.

Site Inspection Photos

Monument #1	Monument #1	Monument #2
Monument #2	Monument #3	Monument #3
Monument #4	Monument #4

Baseline Measurement Photos

You can download high resolution photos taken during the measurement of the Modesto Baseline.

Larry Fontana (Stanislaus County) prepares to take a distance measurement.	Chris Martin (KSN) level a prism over one of the baseline monuments.	A veiw of the calibration baseline site looking east early on the second work day.
Chris Martin (KSN) verifies the tribrach is over the punch mark on one of the calibration baseline monuments.	The prism set-up over Monument #2.	Chris Martin (KSN) watches over the prism and metrological instruments at Monument #2.
Lary Fontana (Stanislaus County) and Alfredo Mijango verify the tribrach is over the punch mark at Monument #3.	A veiw of the calibration baseline site looking east.	A veiw of the calibration baseline site looking west.
Lary Fontana (Stanislaus County) verifies the tribrach is over the punch mark at Monument #3.	Chris Martin (KSN) measures a distance from Monument #1.	The team poses for a group photo at Monument #4 at the end of the second work day.
The team poses for a group photo at Monument #4 at the end of the second work day.